diff --git a/.circleci/config.yml b/.circleci/config.yml
index efd311b7..dc5afa57 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -3,8 +3,9 @@ jobs:
   fce:
     docker:
       - image: circleci/rust:latest
+    resource_class: xlarge
     environment:
-      RUST_BACKTRACE: 1
+      RUST_BACKTRACE: full
       #RUST_TEST_THREADS: 1
     steps:
       - checkout
diff --git a/Cargo.lock b/Cargo.lock
index 9ded3f9e..08012c22 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -781,6 +781,7 @@ dependencies = [
  "serde",
  "serde_derive",
  "serde_json",
+ "thiserror",
  "toml",
  "wasmer-interface-types-fl",
  "wasmer-runtime-core-fl",
diff --git a/aquamarine-vm/src/aquamarine_stepper_vm.rs b/aquamarine-vm/src/aquamarine_stepper_vm.rs
index 87f20ed0..d5788ab3 100644
--- a/aquamarine-vm/src/aquamarine_stepper_vm.rs
+++ b/aquamarine-vm/src/aquamarine_stepper_vm.rs
@@ -18,7 +18,7 @@ use crate::{Result, IType, CallServiceClosure};
 use crate::AquamarineVMError;
 use crate::config::AquamarineVMConfig;
 
-use fluence_faas::{FaaSConfig, HostExportedFunc};
+use fluence_faas::{FaaSConfig, HostExportedFunc, ModuleDescriptor};
 use fluence_faas::FluenceFaaS;
 use fluence_faas::HostImportDescriptor;
 use fluence_faas::IValue;
@@ -180,10 +180,10 @@ fn call_service_descriptor(
     }
 }
 
-/// Splits given path into its directory and file stem
+/// Splits given path into its directory and file name
 ///
 /// # Example
-/// For path `/path/to/aquamarine.wasm` result will be `Ok(PathBuf(/path/to), "aquamarine")`
+/// For path `/path/to/aquamarine.wasm` result will be `Ok(PathBuf(/path/to), "aquamarine.wasm")`
 fn split_dirname(path: PathBuf) -> Result<(PathBuf, String)> {
     use AquamarineVMError::InvalidAquamarinePath;
 
@@ -201,16 +201,16 @@ fn split_dirname(path: PathBuf) -> Result<(PathBuf, String)> {
         });
     }
 
-    let file_stem = path
-        .file_stem()
+    let file_name = path
+        .file_name()
         .expect("checked to be a file, file name must be defined");
-    let file_stem = file_stem.to_string_lossy().into_owned();
+    let file_name = file_name.to_string_lossy().into_owned();
 
     let mut path = path;
     // drop file name from path
     path.pop();
 
-    Ok((path, file_stem))
+    Ok((path, file_name))
 }
 
 fn make_faas_config(
@@ -242,7 +242,11 @@ fn make_faas_config(
 
     FaaSConfig {
         modules_dir: Some(aquamarine_wasm_dir),
-        modules_config: vec![(String::from(aquamarine_wasm_file), aquamarine_module_config)],
+        modules_config: vec![ModuleDescriptor {
+            file_name: String::from(aquamarine_wasm_file),
+            import_name: String::from(aquamarine_wasm_file),
+            config: aquamarine_module_config,
+        }],
         default_modules_config: None,
     }
 }
diff --git a/crates/wit-parser/src/extractor.rs b/crates/wit-parser/src/extractor.rs
index 9e784397..64ab4724 100644
--- a/crates/wit-parser/src/extractor.rs
+++ b/crates/wit-parser/src/extractor.rs
@@ -21,9 +21,9 @@ pub use functions::*;
 pub use wit::*;
 
 use crate::Result;
-use std::path::PathBuf;
+use std::path::Path;
 
-pub fn module_interface(module_path: PathBuf) -> Result<ServiceInterface> {
+pub fn module_interface(module_path: &Path) -> Result<ServiceInterface> {
     use fce_wit_interfaces::FCEWITInterfaces;
 
     let wit_section_bytes = extract_wit_section_bytes(module_path)?;
diff --git a/crates/wit-parser/src/extractor/wit.rs b/crates/wit-parser/src/extractor/wit.rs
index 291e441e..ccca43bc 100644
--- a/crates/wit-parser/src/extractor/wit.rs
+++ b/crates/wit-parser/src/extractor/wit.rs
@@ -21,11 +21,11 @@ use walrus::{IdsToIndices, ModuleConfig};
 use wasmer_wit::ast::Interfaces;
 use wasmer_core::Module as WasmerModule;
 
-use std::path::PathBuf;
+use std::path::Path;
 
 /// Extracts WIT section of provided Wasm binary and converts it to a string.
-pub fn extract_text_wit(wasm_file_path: PathBuf) -> Result<String, WITParserError> {
-    let wit_section_bytes = extract_wit_section_bytes(wasm_file_path)?;
+pub fn extract_text_wit(wasm_file_path: &Path) -> Result<String, WITParserError> {
+    let wit_section_bytes = extract_wit_section_bytes(&wasm_file_path)?;
     let wit = extract_wit_with_fn(&wit_section_bytes)?;
     Ok((&wit).to_string())
 }
@@ -53,9 +53,7 @@ pub(crate) fn extract_wit_with_fn(
     }
 }
 
-pub(crate) fn extract_wit_section_bytes(
-    wasm_file_path: PathBuf,
-) -> Result<Vec<u8>, WITParserError> {
+pub(crate) fn extract_wit_section_bytes(wasm_file_path: &Path) -> Result<Vec<u8>, WITParserError> {
     let module = ModuleConfig::new()
         .parse_file(wasm_file_path)
         .map_err(WITParserError::CorruptedWasmFile)?;
diff --git a/engine/src/engine.rs b/engine/src/engine.rs
index 129d83fe..297233b7 100644
--- a/engine/src/engine.rs
+++ b/engine/src/engine.rs
@@ -65,16 +65,16 @@ impl FCE {
     /// Load a new module inside FCE.
     pub fn load_module<S: Into<String>>(
         &mut self,
-        name: S,
+        import_name: S,
         wasm_bytes: &[u8],
         config: FCEModuleConfig,
     ) -> Result<()> {
-        self.load_module_(name.into(), wasm_bytes, config)
+        self.load_module_(import_name.into(), wasm_bytes, config)
     }
 
     fn load_module_(
         &mut self,
-        name: String,
+        import_name: String,
         wasm_bytes: &[u8],
         config: FCEModuleConfig,
     ) -> Result<()> {
@@ -82,7 +82,7 @@ impl FCE {
 
         let module = FCEModule::new(&wasm_bytes, config, &self.modules)?;
 
-        match self.modules.entry(name) {
+        match self.modules.entry(import_name) {
             Entry::Vacant(entry) => {
                 entry.insert(module);
                 Ok(())
diff --git a/fluence-app-service/src/lib.rs b/fluence-app-service/src/lib.rs
index 43b5c41c..c55a0bd3 100644
--- a/fluence-app-service/src/lib.rs
+++ b/fluence-app-service/src/lib.rs
@@ -48,9 +48,9 @@ pub use fluence_faas::TomlFaaSConfig;
 pub use fluence_faas::TomlFaaSModuleConfig;
 pub use fluence_faas::TomlFaaSNamedModuleConfig;
 pub use fluence_faas::TomlWASIConfig;
+pub use fluence_faas::ModuleDescriptor;
 pub use fluence_faas::from_toml_faas_config;
 pub use fluence_faas::from_toml_module_config;
-pub use fluence_faas::from_toml_named_module_config;
 pub use fluence_faas::from_toml_wasi_config;
 
 pub use fluence_faas::FaaSError;
diff --git a/fluence-app-service/src/service.rs b/fluence-app-service/src/service.rs
index 8d3b41a5..ceddf89b 100644
--- a/fluence-app-service/src/service.rs
+++ b/fluence-app-service/src/service.rs
@@ -55,7 +55,7 @@ impl AppService {
                     "config should contain at least one module",
                 ))
             })?
-            .0
+            .import_name
             .clone();
 
         let service_id = service_id.into();
@@ -150,9 +150,11 @@ impl AppService {
             service_id.into_bytes(),
         );
 
-        for (_, module_config) in &mut config.faas_config.modules_config {
-            module_config.extend_wasi_envs(envs.clone());
-            module_config.extend_wasi_files(preopened_files.clone(), mapped_dirs.clone());
+        for module in &mut config.faas_config.modules_config {
+            module.config.extend_wasi_envs(envs.clone());
+            module
+                .config
+                .extend_wasi_files(preopened_files.clone(), mapped_dirs.clone());
         }
 
         Ok(())
diff --git a/fluence-faas/Cargo.toml b/fluence-faas/Cargo.toml
index 45836c95..ed98f4af 100644
--- a/fluence-faas/Cargo.toml
+++ b/fluence-faas/Cargo.toml
@@ -25,6 +25,7 @@ itertools = "0.9.0"
 cmd_lib = "0.7.8"
 log = "0.4.8"
 safe-transmute = "0.11.0"
+thiserror = "1.0.23"
 
 [dev-dependencies]
 once_cell = "1.4.0"
diff --git a/fluence-faas/src/config.rs b/fluence-faas/src/config.rs
index 4dd727e0..4f7a343b 100644
--- a/fluence-faas/src/config.rs
+++ b/fluence-faas/src/config.rs
@@ -18,7 +18,15 @@ use fce::HostImportDescriptor;
 
 use std::collections::HashMap;
 use std::collections::HashSet;
-use std::path::PathBuf;
+use std::path::{PathBuf};
+
+/// Info to load a module from filesystem into runtime.
+#[derive(Default)]
+pub struct ModuleDescriptor {
+    pub file_name: String,
+    pub import_name: String,
+    pub config: FaaSModuleConfig,
+}
 
 /// Describes the behaviour of FluenceFaaS.
 #[derive(Default)]
@@ -27,7 +35,7 @@ pub struct FaaSConfig {
     pub modules_dir: Option<PathBuf>,
 
     /// Settings for a module with particular name (not HashMap because the order is matter).
-    pub modules_config: Vec<(String, FaaSModuleConfig)>,
+    pub modules_config: Vec<ModuleDescriptor>,
 
     /// Settings for a module that name's not been found in modules_config.
     pub default_modules_config: Option<FaaSModuleConfig>,
diff --git a/fluence-faas/src/errors.rs b/fluence-faas/src/errors.rs
index b9430a18..983cbcda 100644
--- a/fluence-faas/src/errors.rs
+++ b/fluence-faas/src/errors.rs
@@ -17,66 +17,59 @@
 use fce::FCEError;
 
 use std::io::Error as IOError;
-use std::error::Error;
+use thiserror::Error;
+use std::path::PathBuf;
 
-#[derive(Debug)]
+#[derive(Debug, Error)]
 pub enum FaaSError {
-    /// An error related to config parsing.
-    ConfigParseError(String),
+    /// Errors that happened due to invalid config content
+    #[error("InvalidConfig: {0}")]
+    InvalidConfig(String),
 
     /// An error occurred at the instantiation step.
-    InstantiationError(String),
+    #[error(
+        "module with name {module_import_name} is specified in config (dir: {modules_dir:?}), \
+         but not found in provided modules: {provided_modules:?}"
+    )]
+    InstantiationError {
+        module_import_name: String,
+        modules_dir: Option<PathBuf>,
+        provided_modules: Vec<String>,
+    },
 
     /// Various errors related to file i/o.
+    #[error("IOError: {0}")]
     IOError(String),
 
     /// A function with specified name is missing.
+    #[error("function with name `{0}` is missing")]
     MissingFunctionError(String),
 
     /// An argument with specified name is missing.
+    #[error(r#"argument with name "{0}" is missing"#)]
     MissingArgumentError(String),
 
     /// Returns when there is no module with such name.
+    #[error(r#"module with name "{0}" is missing"#)]
     NoSuchModule(String),
 
     /// Provided arguments aren't compatible with a called function signature.
+    #[error("JsonArgumentsDeserializationError: {0}")]
     JsonArgumentsDeserializationError(String),
 
     /// Returned outputs aren't compatible with a called function signature.
+    #[error("JsonOutputSerializationError: {0}")]
     JsonOutputSerializationError(String),
 
     /// Errors related to invalid config.
+    #[error("ParseConfigError: {0}")]
     ParseConfigError(toml::de::Error),
 
     /// FCE errors.
+    #[error("EngineError: {0}")]
     EngineError(FCEError),
 }
 
-impl Error for FaaSError {}
-
-impl std::fmt::Display for FaaSError {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
-        match self {
-            FaaSError::ConfigParseError(err_msg) => write!(f, "{}", err_msg),
-            FaaSError::InstantiationError(err_msg) => write!(f, "{}", err_msg),
-            FaaSError::MissingFunctionError(func_name) => {
-                write!(f, "function with name `{}` is missing", func_name)
-            }
-            FaaSError::MissingArgumentError(arg_name) => {
-                write!(f, r#"argument with name "{}" is missing"#, arg_name)
-            }
-            FaaSError::NoSuchModule(module_name) => {
-                write!(f, r#"module with name "{}" is missing"#, module_name)
-            }
-            FaaSError::JsonArgumentsDeserializationError(args) => write!(f, "{}", args),
-            FaaSError::JsonOutputSerializationError(args) => write!(f, "{}", args),
-            FaaSError::IOError(err_msg) => write!(f, "{}", err_msg),
-            FaaSError::EngineError(err) => write!(f, "{}", err),
-            FaaSError::ParseConfigError(err) => write!(f, "{}", err),
-        }
-    }
-}
-
 impl From<IOError> for FaaSError {
     fn from(err: IOError) -> Self {
         FaaSError::IOError(format!("{}", err))
@@ -91,7 +84,7 @@ impl From<FCEError> for FaaSError {
 
 impl From<toml::de::Error> for FaaSError {
     fn from(err: toml::de::Error) -> Self {
-        FaaSError::ConfigParseError(format!("{}", err))
+        FaaSError::ParseConfigError(err)
     }
 }
 
diff --git a/fluence-faas/src/faas.rs b/fluence-faas/src/faas.rs
index 12bc6922..9c572b4a 100644
--- a/fluence-faas/src/faas.rs
+++ b/fluence-faas/src/faas.rs
@@ -34,10 +34,8 @@ use fluence_sdk_main::CallParameters;
 use serde_json::Value as JValue;
 use std::cell::RefCell;
 use std::convert::TryInto;
-use std::collections::HashSet;
 use std::collections::HashMap;
 use std::rc::Rc;
-use std::path::PathBuf;
 
 struct ModuleInterface {
     function_signatures: HashMap<SharedString, (Rc<Vec<IFunctionArg>>, Rc<Vec<IType>>)>,
@@ -59,12 +57,6 @@ pub struct FluenceFaaS {
 }
 
 impl FluenceFaaS {
-    /// Creates FaaS from config on filesystem.
-    pub fn with_config_path<P: Into<PathBuf>>(config_file_path: P) -> Result<Self> {
-        let config = crate::raw_toml_config::TomlFaaSConfig::load(config_file_path.into())?;
-        Self::with_raw_config(config)
-    }
-
     /// Creates FaaS from config deserialized from TOML.
     pub fn with_raw_config<C>(config: C) -> Result<Self>
     where
@@ -73,13 +65,11 @@ impl FluenceFaaS {
     {
         let config = config.try_into()?;
         let modules = config
-            .modules_dir
-            .as_ref()
-            .map_or(Ok(HashMap::new()), |dir| {
-                load_modules_from_fs(dir, ModulesLoadStrategy::WasmOnly)
-            })?;
-
-        Self::with_modules::<FaaSConfig>(modules, config)
+            .modules_config
+            .iter()
+            .map(|m| (m.file_name.clone(), m.import_name.clone()))
+            .collect();
+        Self::with_module_names::<FaaSConfig>(&modules, config)
     }
 
     /// Creates FaaS with given modules.
@@ -98,22 +88,22 @@ impl FluenceFaaS {
         let wasm_log_env = std::env::var(WASM_LOG_ENV_NAME).unwrap_or_default();
         let logger_filter = LoggerFilter::from_env_string(&wasm_log_env);
 
-        for (module_name, module_config) in config.modules_config {
-            let module_bytes =
-                modules.remove(&module_name).ok_or_else(|| {
-                    FaaSError::InstantiationError(format!(
-                    "module with name {} is specified in config (dir: {:?}), but not found in provided modules: {:?}",
-                    module_name, modules_dir, modules.keys().collect::<Vec<_>>()
-                ))
-                })?;
+        for module in config.modules_config {
+            let module_bytes = modules.remove(&module.import_name).ok_or_else(|| {
+                FaaSError::InstantiationError {
+                    module_import_name: module.import_name.clone(),
+                    modules_dir: modules_dir.clone(),
+                    provided_modules: modules.keys().cloned().collect::<Vec<_>>(),
+                }
+            })?;
 
             let fce_module_config = crate::misc::make_fce_config(
-                module_name.clone(),
-                Some(module_config),
+                module.import_name.clone(),
+                Some(module.config),
                 call_parameters.clone(),
                 &logger_filter,
             )?;
-            fce.load_module(module_name, &module_bytes, fce_module_config)?;
+            fce.load_module(module.import_name, &module_bytes, fce_module_config)?;
         }
 
         Ok(Self {
@@ -124,7 +114,7 @@ impl FluenceFaaS {
     }
 
     /// Searches for modules in `config.modules_dir`, loads only those in the `names` set
-    pub fn with_module_names<C>(names: &HashSet<String>, config: C) -> Result<Self>
+    pub fn with_module_names<C>(names: &HashMap<String, String>, config: C) -> Result<Self>
     where
         C: TryInto<FaaSConfig>,
         FaaSError: From<C::Error>,
diff --git a/fluence-faas/src/lib.rs b/fluence-faas/src/lib.rs
index 54fd1822..cfaa62ce 100644
--- a/fluence-faas/src/lib.rs
+++ b/fluence-faas/src/lib.rs
@@ -41,6 +41,7 @@ pub use faas_interface::itype_text_view;
 pub use config::FaaSConfig;
 pub use config::FaaSModuleConfig;
 pub use config::FaaSWASIConfig;
+pub use config::ModuleDescriptor;
 
 pub use raw_toml_config::TomlFaaSConfig;
 pub use raw_toml_config::TomlFaaSModuleConfig;
@@ -48,7 +49,6 @@ pub use raw_toml_config::TomlFaaSNamedModuleConfig;
 pub use raw_toml_config::TomlWASIConfig;
 pub use raw_toml_config::from_toml_faas_config;
 pub use raw_toml_config::from_toml_module_config;
-pub use raw_toml_config::from_toml_named_module_config;
 pub use raw_toml_config::from_toml_wasi_config;
 
 pub use errors::FaaSError;
diff --git a/fluence-faas/src/misc/modules_load_strategy.rs b/fluence-faas/src/misc/modules_load_strategy.rs
index 88e62cd6..5d4bfa78 100644
--- a/fluence-faas/src/misc/modules_load_strategy.rs
+++ b/fluence-faas/src/misc/modules_load_strategy.rs
@@ -15,16 +15,25 @@
  */
 
 use std::path::Path;
-use std::collections::HashSet;
+use std::collections::{HashMap, HashSet};
+use crate::FaaSError;
+use std::ffi::OsStr;
+use std::borrow::Cow;
+
+type ImportName = String;
+type FileName = String;
 
 /// Strategies for module loading.
+#[derive(Debug, Clone)]
 pub enum ModulesLoadStrategy<'a> {
-    /// Try to load all files in a given directory
+    /// Load all files in a given directory
     #[allow(dead_code)]
     All,
-    /// Try to load only files contained in the set
-    Named(&'a HashSet<String>),
+    /// Load only files contained in the set
+    /// Correspondence between module file name and import name is crucial for `extract_module_name`
+    Named(&'a HashMap<FileName, ImportName>),
     /// In a given directory, try to load all files ending with .wasm
+    #[allow(dead_code)]
     WasmOnly,
 }
 
@@ -34,7 +43,7 @@ impl<'a> ModulesLoadStrategy<'a> {
     pub fn should_load(&self, module: &Path) -> bool {
         match self {
             ModulesLoadStrategy::All => true,
-            ModulesLoadStrategy::Named(set) => set.contains(module.to_string_lossy().as_ref()),
+            ModulesLoadStrategy::Named(map) => map.contains_key(module.to_string_lossy().as_ref()),
             ModulesLoadStrategy::WasmOnly => module.extension().map_or(false, |e| e == "wasm"),
         }
     }
@@ -50,28 +59,46 @@ impl<'a> ModulesLoadStrategy<'a> {
 
     #[inline]
     /// Returns difference between required and loaded modules.
-    pub fn missing_modules<'s>(&self, loaded: impl Iterator<Item = &'s String>) -> Vec<&'s String> {
+    pub fn missing_modules<'i>(
+        &self,
+        loaded: impl Iterator<Item = &'i String>,
+    ) -> HashSet<&String> {
         match self {
-            ModulesLoadStrategy::Named(set) => loaded.fold(vec![], |mut vec, module| {
-                if !set.contains(module) {
-                    vec.push(module)
-                }
-                vec
-            }),
+            ModulesLoadStrategy::Named(map) => {
+                let set: HashSet<_> = map.keys().collect();
+                loaded.fold(set, |mut set, module| {
+                    set.remove(module);
+                    set
+                })
+            }
             _ => <_>::default(),
         }
     }
 
     #[inline]
-    pub fn extract_module_name(&self, module: String) -> String {
+    pub fn extract_module_name(&self, module_path: &Path) -> Result<String, FaaSError> {
+        use FaaSError::*;
+
+        fn as_str<'a>(
+            os_str: Option<&'a OsStr>,
+            path: &'a Path,
+        ) -> Result<Cow<'a, str>, FaaSError> {
+            os_str
+                .map(|s| s.to_string_lossy())
+                .ok_or_else(|| IOError(format!("No file name in path {:?}", path)))
+        }
+
         match self {
-            ModulesLoadStrategy::WasmOnly => {
-                let path: &Path = module.as_ref();
-                path.file_stem()
-                    .map(|s| s.to_string_lossy().to_string())
-                    .unwrap_or(module)
+            Self::Named(map) => {
+                let file_name = as_str(module_path.file_name(), module_path)?;
+                // Take import_name from the mapping and return it
+                let import_name = map.get(file_name.as_ref());
+                let import_name = import_name.ok_or_else(|| NoSuchModule(file_name.to_string()))?;
+
+                Ok(import_name.clone())
             }
-            _ => module,
+            // for other strategies, simply use file name without extension
+            _ => Ok(as_str(module_path.file_stem(), module_path)?.to_string()),
         }
     }
 }
diff --git a/fluence-faas/src/misc/utils.rs b/fluence-faas/src/misc/utils.rs
index ccd05248..7c50feda 100644
--- a/fluence-faas/src/misc/utils.rs
+++ b/fluence-faas/src/misc/utils.rs
@@ -32,7 +32,7 @@ use wasmer_wit::IType;
 
 use std::collections::HashMap;
 use std::cell::RefCell;
-use std::path::PathBuf;
+use std::path::{PathBuf, Path};
 use std::rc::Rc;
 use std::ops::Deref;
 
@@ -176,18 +176,16 @@ pub(crate) fn load_modules_from_fs(
             return Ok(hash_map);
         }
 
-        let module_name = path
-            .file_name()
-            .ok_or_else(|| IOError(format!("No file name in path {:?}", path)))?
-            .to_os_string()
-            .into_string()
-            .map_err(|name| IOError(format!("invalid file name: {:?}", name)))?;
+        let file_name = Path::new(
+            path.file_name()
+                .ok_or_else(|| IOError(format!("No file name in path {:?}", path)))?,
+        );
 
-        if modules.should_load(&module_name.as_ref()) {
-            let module_bytes = std::fs::read(path)?;
-            let module_name = modules.extract_module_name(module_name);
+        if modules.should_load(&file_name) {
+            let module_bytes = std::fs::read(&path)?;
+            let module_name = modules.extract_module_name(&path)?;
             if hash_map.insert(module_name, module_bytes).is_some() {
-                return Err(FaaSError::ConfigParseError(String::from(
+                return Err(FaaSError::InvalidConfig(String::from(
                     "module {} is duplicated in config",
                 )));
             }
@@ -199,7 +197,7 @@ pub(crate) fn load_modules_from_fs(
     if modules.required_modules_len() > loaded.len() {
         let loaded = loaded.iter().map(|(n, _)| n);
         let not_found = modules.missing_modules(loaded);
-        return Err(FaaSError::ConfigParseError(format!(
+        return Err(FaaSError::InvalidConfig(format!(
             "the following modules were not found: {:?}",
             not_found
         )));
diff --git a/fluence-faas/src/raw_toml_config.rs b/fluence-faas/src/raw_toml_config.rs
index 6fdc9579..e35edcae 100644
--- a/fluence-faas/src/raw_toml_config.rs
+++ b/fluence-faas/src/raw_toml_config.rs
@@ -25,6 +25,7 @@ use std::convert::TryInto;
 use std::collections::HashMap;
 use std::collections::HashSet;
 use std::path::PathBuf;
+use serde::export::TryFrom;
 
 /*
 An example of the config:
@@ -72,9 +73,7 @@ impl TomlFaaSConfig {
     pub fn load<P: Into<PathBuf>>(path: P) -> Result<Self> {
         let path = path.into();
         let file_content = std::fs::read(&path)?;
-        toml::from_slice(&file_content).map_err(|e| {
-            FaaSError::ConfigParseError(format!("Error parsing config {:?}: {:?}", path, e))
-        })
+        Ok(toml::from_slice(&file_content)?)
     }
 }
 
@@ -89,23 +88,21 @@ impl TryInto<FaaSConfig> for TomlFaaSConfig {
 #[derive(Deserialize, Serialize, Debug, Clone, Default)]
 pub struct TomlFaaSNamedModuleConfig {
     pub name: String,
+    #[serde(default)]
+    pub file_name: Option<String>,
     #[serde(flatten)]
     pub config: TomlFaaSModuleConfig,
 }
 
-impl TryInto<(String, FaaSModuleConfig)> for TomlFaaSNamedModuleConfig {
+impl TryFrom<TomlFaaSNamedModuleConfig> for ModuleDescriptor {
     type Error = FaaSError;
 
-    fn try_into(self) -> Result<(String, FaaSModuleConfig)> {
-        from_toml_named_module_config(self)
-    }
-}
-
-impl TryInto<FaaSModuleConfig> for TomlFaaSNamedModuleConfig {
-    type Error = FaaSError;
-
-    fn try_into(self) -> Result<FaaSModuleConfig> {
-        from_toml_named_module_config(self).map(|(_, module_config)| module_config)
+    fn try_from(config: TomlFaaSNamedModuleConfig) -> Result<Self> {
+        Ok(ModuleDescriptor {
+            file_name: config.file_name.unwrap_or(format!("{}.wasm", config.name)),
+            import_name: config.name,
+            config: from_toml_module_config(config.config)?,
+        })
     }
 }
 
@@ -118,18 +115,6 @@ pub struct TomlFaaSModuleConfig {
     pub logging_mask: Option<i32>,
 }
 
-impl TomlFaaSNamedModuleConfig {
-    pub fn new<S>(name: S) -> Self
-    where
-        S: Into<String>,
-    {
-        Self {
-            name: name.into(),
-            config: <_>::default(),
-        }
-    }
-}
-
 #[derive(Deserialize, Serialize, Debug, Clone, Default)]
 pub struct TomlWASIConfig {
     pub preopened_files: Option<Vec<String>>,
@@ -142,7 +127,7 @@ pub fn from_toml_faas_config(config: TomlFaaSConfig) -> Result<FaaSConfig> {
     let modules_config = config
         .module
         .into_iter()
-        .map(from_toml_named_module_config)
+        .map(ModuleDescriptor::try_from)
         .collect::<Result<Vec<_>>>()?;
 
     let default_modules_config = config.default.map(from_toml_module_config).transpose()?;
@@ -154,13 +139,6 @@ pub fn from_toml_faas_config(config: TomlFaaSConfig) -> Result<FaaSConfig> {
     })
 }
 
-pub fn from_toml_named_module_config(
-    config: TomlFaaSNamedModuleConfig,
-) -> Result<(String, FaaSModuleConfig)> {
-    let module_config = from_toml_module_config(config.config)?;
-    Ok((config.name, module_config))
-}
-
 pub fn from_toml_module_config(config: TomlFaaSModuleConfig) -> Result<FaaSModuleConfig> {
     let mounted_binaries = config.mounted_binaries.unwrap_or_default();
     let mounted_binaries = mounted_binaries
@@ -236,6 +214,7 @@ mod tests {
     fn serialize_named() {
         let config = TomlFaaSNamedModuleConfig {
             name: "name".to_string(),
+            file_name: Some("file_name".to_string()),
             config: TomlFaaSModuleConfig {
                 mem_pages_count: Some(100),
                 logger_enabled: Some(false),
diff --git a/tools/cli/src/main.rs b/tools/cli/src/main.rs
index 301140d8..af1e3fa8 100644
--- a/tools/cli/src/main.rs
+++ b/tools/cli/src/main.rs
@@ -70,9 +70,9 @@ pub fn main() -> std::result::Result<(), anyhow::Error> {
         }
         ("show", Some(arg)) => {
             let wasm_path = arg.value_of(args::IN_WASM_PATH).unwrap();
-            let wasm_path = std::path::PathBuf::from(wasm_path);
+            let wasm_path = std::path::Path::new(wasm_path);
 
-            let result = fce_wit_parser::extract_text_wit(wasm_path)?;
+            let result = fce_wit_parser::extract_text_wit(&wasm_path)?;
             println!("{}", result);
 
             Ok(())