diff --git a/.circleci/config.yml b/.circleci/config.yml
index 756e0e6f..bcf17f7e 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -54,12 +54,12 @@ jobs:
           cd examples/ipfs_node/wasm/ipfs_node
           cargo fmt --all -- --check --color always
           cargo wasi build
-          cargo clippy -v
+          cargo clippy -v --target wasm32-wasi
 
           cd ../ipfs_rpc
           cargo fmt --all -- --check --color always
           cargo wasi build
-          cargo clippy -v
+          cargo clippy -v --target wasm32-wasi
 
 #          cd ../../../../tools/wit_embedder
 #          cargo fmt --all -- --check --color always
diff --git a/crates/wit-generator/src/instructions_generator/foreign_mod_instructions.rs b/crates/wit-generator/src/instructions_generator/foreign_mod_instructions.rs
index c532c3a3..010f5aee 100644
--- a/crates/wit-generator/src/instructions_generator/foreign_mod_instructions.rs
+++ b/crates/wit-generator/src/instructions_generator/foreign_mod_instructions.rs
@@ -26,8 +26,15 @@ use fluence_sdk_wit::ParsedType;
 use wasmer_wit::interpreter::Instruction;
 use crate::instructions_generator::utils::wtype_to_itype;
 
+const HOST_NAMESPACE_NAME: &str = "host";
+
 impl WITGenerator for AstExternModItem {
     fn generate_wit<'a>(&'a self, interfaces: &mut Interfaces<'a>) {
+        // host imports should be left as is
+        if self.namespace == HOST_NAMESPACE_NAME {
+            return;
+        }
+
         for import in &self.imports {
             generate_wit_for_import(import, &self.namespace, interfaces);
         }
diff --git a/crates/wit-generator/src/instructions_generator/utils.rs b/crates/wit-generator/src/instructions_generator/utils.rs
index d728cae6..e1583463 100644
--- a/crates/wit-generator/src/instructions_generator/utils.rs
+++ b/crates/wit-generator/src/instructions_generator/utils.rs
@@ -32,7 +32,7 @@ pub(crate) fn ptype_to_itype(pty: &ParsedType) -> IType {
         ParsedType::F64 => IType::F64,
         ParsedType::Boolean => IType::I32,
         ParsedType::Utf8String => IType::String,
-        ParsedType::ByteVector => IType::String,
+        ParsedType::ByteVector => IType::ByteArray,
         ParsedType::Record(_) => unimplemented!(),
     }
 }
diff --git a/engine/src/engine.rs b/engine/src/engine.rs
index e0f5d7a2..a41df11e 100644
--- a/engine/src/engine.rs
+++ b/engine/src/engine.rs
@@ -47,29 +47,44 @@ impl FCE {
         module_name: MN,
         func_name: FN,
         argument: &[IValue],
-    ) -> Result<Vec<IValue>, FCEError> {
-        match self.modules.get_mut(module_name.as_ref()) {
+    ) -> Result<Vec<IValue>> {
+        self.call_(module_name.as_ref(), func_name.as_ref(), argument)
+    }
+
+    pub fn call_(
+        &mut self,
+        module_name: &str,
+        func_name: &str,
+        argument: &[IValue],
+    ) -> Result<Vec<IValue>> {
+        match self.modules.get_mut(module_name) {
             // TODO: refactor errors
             Some(module) => module.call(func_name.as_ref(), argument),
-            None => Err(FCEError::NoSuchModule(module_name.as_ref().to_string())),
+            None => Err(FCEError::NoSuchModule(module_name.to_string())),
         }
     }
 
     /// Load a new module inside FCE.
-    pub fn load_module<S>(
+    pub fn load_module<S: Into<String>>(
         &mut self,
         module_name: S,
         wasm_bytes: &[u8],
         config: FCEModuleConfig,
-    ) -> Result<(), FCEError>
-    where
-        S: Into<String>,
-    {
+    ) -> Result<()> {
+        self.load_module_(module_name.into(), wasm_bytes, config)
+    }
+
+    pub fn load_module_(
+        &mut self,
+        module_name: String,
+        wasm_bytes: &[u8],
+        config: FCEModuleConfig,
+    ) -> Result<()> {
         let _prepared_wasm_bytes = crate::misc::prepare_module(wasm_bytes, config.mem_pages_count)?;
 
         let module = FCEModule::new(&wasm_bytes, config, &self.modules)?;
 
-        match self.modules.entry(module_name.into()) {
+        match self.modules.entry(module_name) {
             Entry::Vacant(entry) => {
                 entry.insert(module);
                 Ok(())
@@ -79,10 +94,14 @@ impl FCE {
     }
 
     /// Unload previously loaded module.
-    pub fn unload_module<S: AsRef<str>>(&mut self, module_name: S) -> Result<(), FCEError> {
-        match self.modules.remove(module_name.as_ref()) {
+    pub fn unload_module<S: AsRef<str>>(&mut self, module_name: S) -> Result<()> {
+        self.unload_module_(module_name.as_ref())
+    }
+
+    pub fn unload_module_(&mut self, module_name: &str) -> Result<()> {
+        match self.modules.remove(module_name) {
             Some(_) => Ok(()),
-            None => Err(FCEError::NoSuchModule(module_name.as_ref().to_string())),
+            None => Err(FCEError::NoSuchModule(module_name.to_string())),
         }
     }
 
@@ -100,7 +119,7 @@ impl FCE {
     pub fn module_interface<S: AsRef<str>>(
         &self,
         module_name: S,
-    ) -> Result<Vec<FCEFunctionSignature<'_>>, FCEError> {
+    ) -> Result<Vec<FCEFunctionSignature<'_>>> {
         match self.modules.get(module_name.as_ref()) {
             Some(module) => Ok(Self::get_module_function_signatures(module)),
             None => Err(FCEError::NoSuchModule(module_name.as_ref().to_string())),
diff --git a/engine/src/lib.rs b/engine/src/lib.rs
index b65afd77..b0dd5ec4 100644
--- a/engine/src/lib.rs
+++ b/engine/src/lib.rs
@@ -39,4 +39,7 @@ pub use engine::FCEFunctionSignature;
 pub use errors::FCEError;
 pub use module::IValue;
 pub use module::IType;
-pub use module::{to_interface_value, from_interface_values};
+pub use module::from_interface_values;
+pub use module::to_interface_value;
+
+pub(crate) type Result<T> = std::result::Result<T, FCEError>;
diff --git a/engine/src/misc/prepare.rs b/engine/src/misc/prepare.rs
index a60b51b2..357860f8 100644
--- a/engine/src/misc/prepare.rs
+++ b/engine/src/misc/prepare.rs
@@ -18,7 +18,7 @@
 // https://github.com/paritytech/substrate/blob/master/srml/contracts/src/wasm/prepare.rs
 // https://github.com/nearprotocol/nearcore/blob/master/runtime/near-vm-runner/src/prepare.rs
 
-use crate::FCEError;
+use crate::Result;
 
 use parity_wasm::{
     builder, elements,
@@ -30,7 +30,7 @@ struct ModuleBootstrapper {
 }
 
 impl<'a> ModuleBootstrapper {
-    fn init(module_code: &[u8]) -> Result<Self, FCEError> {
+    fn init(module_code: &[u8]) -> Result<Self> {
         let module = elements::deserialize_buffer(module_code)?;
 
         Ok(Self { module })
@@ -66,14 +66,14 @@ impl<'a> ModuleBootstrapper {
         }
     }
 
-    fn into_wasm(self) -> Result<Vec<u8>, FCEError> {
+    fn into_wasm(self) -> Result<Vec<u8>> {
         elements::serialize(self.module).map_err(Into::into)
     }
 }
 
 /// Prepares a Wasm module:
 ///   - set memory page count
-pub(crate) fn prepare_module(module: &[u8], mem_pages_count: u32) -> Result<Vec<u8>, FCEError> {
+pub(crate) fn prepare_module(module: &[u8], mem_pages_count: u32) -> Result<Vec<u8>> {
     ModuleBootstrapper::init(module)?
         .set_mem_pages_count(mem_pages_count)
         .into_wasm()
diff --git a/engine/src/module/exports.rs b/engine/src/module/exports.rs
index 322b1f86..b0d34e85 100644
--- a/engine/src/module/exports.rs
+++ b/engine/src/module/exports.rs
@@ -14,7 +14,8 @@
  * limitations under the License.
  */
 
-use super::{IValue, IType};
+use super::IValue;
+use super::IType;
 use wasmer_wit::interpreter::wasm;
 
 // In current implementation export simply does nothing, because there is no more
diff --git a/engine/src/module/fce_module.rs b/engine/src/module/fce_module.rs
index 1ce79d3a..eb5f3c2c 100644
--- a/engine/src/module/fce_module.rs
+++ b/engine/src/module/fce_module.rs
@@ -16,13 +16,15 @@
 
 use super::wit_prelude::*;
 use super::{IType, IValue, WValue};
+use crate::Result;
 use crate::FCEModuleConfig;
 
 use fce_wit_interfaces::FCEWITInterfaces;
-use wasmer_wit::interpreter::Interpreter;
-use wasmer_runtime::{compile, ImportObject};
 use wasmer_core::Instance as WasmerInstance;
 use wasmer_core::import::Namespace;
+use wasmer_runtime::compile;
+use wasmer_runtime::ImportObject;
+use wasmer_wit::interpreter::Interpreter;
 use wit_parser::extract_wit;
 
 use std::collections::HashMap;
@@ -47,7 +49,7 @@ pub(super) struct Callable {
 }
 
 impl Callable {
-    pub fn call(&mut self, args: &[IValue]) -> Result<Vec<IValue>, FCEError> {
+    pub fn call(&mut self, args: &[IValue]) -> Result<Vec<IValue>> {
         use wasmer_wit::interpreter::stack::Stackable;
 
         let result = self
@@ -86,7 +88,7 @@ impl FCEModule {
         wasm_bytes: &[u8],
         fce_module_config: FCEModuleConfig,
         modules: &HashMap<String, FCEModule>,
-    ) -> Result<Self, FCEError> {
+    ) -> Result<Self> {
         let wasmer_module = compile(&wasm_bytes)?;
         let wit = extract_wit(&wasmer_module)?;
         let fce_wit = FCEWITInterfaces::new(wit);
@@ -130,11 +132,7 @@ impl FCEModule {
         })
     }
 
-    pub(crate) fn call(
-        &mut self,
-        function_name: &str,
-        args: &[IValue],
-    ) -> Result<Vec<IValue>, FCEError> {
+    pub(crate) fn call(&mut self, function_name: &str, args: &[IValue]) -> Result<Vec<IValue>> {
         match self.exports_funcs.get_mut(function_name) {
             Some(func) => Arc::make_mut(func).call(args),
             None => Err(FCEError::NoSuchFunction(format!(
@@ -157,7 +155,7 @@ impl FCEModule {
     }
 
     // TODO: change the cloning Callable behaviour after changes of Wasmer API
-    pub(super) fn get_callable(&self, function_name: &str) -> Result<Arc<Callable>, FCEError> {
+    pub(super) fn get_callable(&self, function_name: &str) -> Result<Arc<Callable>> {
         match self.exports_funcs.get(function_name) {
             Some(func) => Ok(func.clone()),
             None => Err(FCEError::NoSuchFunction(format!(
@@ -170,7 +168,7 @@ impl FCEModule {
     fn instantiate_wit_exports(
         wit_instance: Arc<WITInstance>,
         wit: &FCEWITInterfaces<'_>,
-    ) -> Result<HashMap<String, Arc<Callable>>, FCEError> {
+    ) -> Result<HashMap<String, Arc<Callable>>> {
         use fce_wit_interfaces::WITAstType;
 
         wit.implementations()
@@ -218,14 +216,14 @@ impl FCEModule {
                     ))),
                 }
             })
-            .collect::<Result<HashMap<String, Arc<Callable>>, FCEError>>()
+            .collect::<Result<HashMap<String, Arc<Callable>>>>()
     }
 
     // this function deals only with import functions that have an adaptor implementation
     fn adjust_wit_imports(
         wit: &FCEWITInterfaces<'_>,
         wit_instance: Arc<MaybeUninit<WITInstance>>,
-    ) -> Result<ImportObject, FCEError> {
+    ) -> Result<ImportObject> {
         use fce_wit_interfaces::WITAstType;
         use wasmer_core::typed_func::DynamicFunc;
         use wasmer_core::vm::Ctx;
@@ -327,7 +325,7 @@ impl FCEModule {
                     ))),
                 }
             })
-            .collect::<Result<multimap::MultiMap<_, _>, FCEError>>()?;
+            .collect::<Result<multimap::MultiMap<_, _>>>()?;
 
         let mut import_object = ImportObject::new();
 
diff --git a/engine/src/module/mod.rs b/engine/src/module/mod.rs
index 00505753..5c21504b 100644
--- a/engine/src/module/mod.rs
+++ b/engine/src/module/mod.rs
@@ -21,11 +21,12 @@ mod wit_instance;
 mod type_converters;
 mod fce_module;
 
-pub(crate) use fce_module::FCEModule;
-
 pub use wasmer_wit::types::InterfaceType as IType;
 pub use wasmer_wit::values::InterfaceValue as IValue;
-pub use wasmer_wit::values::{to_interface_value, from_interface_values};
+pub use wasmer_wit::values::from_interface_values;
+pub use wasmer_wit::values::to_interface_value;
+
+pub(crate) use fce_module::FCEModule;
 pub(self) use wasmer_core::types::Type as WType;
 pub(self) use wasmer_core::types::Value as WValue;
 
diff --git a/engine/src/module/wit_function.rs b/engine/src/module/wit_function.rs
index 27453ed5..ed80e83f 100644
--- a/engine/src/module/wit_function.rs
+++ b/engine/src/module/wit_function.rs
@@ -14,10 +14,10 @@
  * limitations under the License.
  */
 
-use super::wit_prelude::FCEError;
 use super::fce_module::FCEModule;
 use super::{IType, IValue, WValue};
 use super::fce_module::Callable;
+use crate::Result;
 
 use wasmer_wit::interpreter::wasm;
 use wasmer_core::instance::DynFunc;
@@ -45,7 +45,7 @@ pub(super) struct WITFunction {
 
 impl WITFunction {
     /// Creates functions from a "usual" (not WIT) module export.
-    pub(super) fn from_export(dyn_func: DynFunc<'static>) -> Result<Self, FCEError> {
+    pub(super) fn from_export(dyn_func: DynFunc<'static>) -> Result<Self> {
         use super::type_converters::wtype_to_itype;
 
         let signature = dyn_func.signature();
@@ -70,10 +70,7 @@ impl WITFunction {
     }
 
     /// Creates function from a module import.
-    pub(super) fn from_import(
-        wit_module: &FCEModule,
-        function_name: &str,
-    ) -> Result<Self, FCEError> {
+    pub(super) fn from_import(wit_module: &FCEModule, function_name: &str) -> Result<Self> {
         let callable = wit_module.get_callable(function_name)?;
 
         let inner = WITFunctionInner::Import { callable };
@@ -111,7 +108,7 @@ impl wasm::structures::LocalImport for WITFunction {
         }
     }
 
-    fn call(&self, arguments: &[IValue]) -> Result<Vec<IValue>, ()> {
+    fn call(&self, arguments: &[IValue]) -> std::result::Result<Vec<IValue>, ()> {
         use super::type_converters::{ival_to_wval, wval_to_ival};
 
         match &self.inner {
diff --git a/engine/src/module/wit_instance.rs b/engine/src/module/wit_instance.rs
index 1a5f3257..372e2e4a 100644
--- a/engine/src/module/wit_instance.rs
+++ b/engine/src/module/wit_instance.rs
@@ -16,6 +16,7 @@
 
 use super::wit_prelude::*;
 use super::fce_module::FCEModule;
+use crate::Result;
 
 use fce_wit_interfaces::FCEWITInterfaces;
 use fce_wit_interfaces::WITAstType;
@@ -37,7 +38,7 @@ impl WITInstance {
         wasmer_instance: &WasmerInstance,
         wit: &FCEWITInterfaces<'_>,
         modules: &HashMap<String, FCEModule>,
-    ) -> Result<Self, FCEError> {
+    ) -> Result<Self> {
         let mut exports = Self::extract_raw_exports(&wasmer_instance, wit)?;
         let imports = Self::extract_imports(modules, wit, exports.len())?;
         let memories = Self::extract_memories(&wasmer_instance);
@@ -51,7 +52,7 @@ impl WITInstance {
     fn extract_raw_exports(
         wasmer_instance: &WasmerInstance,
         wit: &FCEWITInterfaces<'_>,
-    ) -> Result<HashMap<usize, WITFunction>, FCEError> {
+    ) -> Result<HashMap<usize, WITFunction>> {
         use wasmer_core::DynFunc;
 
         let module_exports = &wasmer_instance.exports;
@@ -76,7 +77,7 @@ impl WITInstance {
         modules: &HashMap<String, FCEModule>,
         wit: &FCEWITInterfaces<'_>,
         start_index: usize,
-    ) -> Result<HashMap<usize, WITFunction>, FCEError> {
+    ) -> Result<HashMap<usize, WITFunction>> {
         wit.imports()
             .filter(|import|
                 // filter out imports that have implementations
@@ -89,7 +90,7 @@ impl WITInstance {
                 }
                 None => Err(FCEError::NoSuchModule(import.namespace.to_string())),
             })
-            .collect::<Result<HashMap<_, _>, _>>()
+            .collect::<Result<HashMap<_, _>>>()
     }
 
     fn extract_memories(wasmer_instance: &WasmerInstance) -> Vec<WITMemory> {
diff --git a/examples/ipfs_node/wasm/artifacts/ipfs_rpc.wasm b/examples/ipfs_node/wasm/artifacts/ipfs_rpc.wasm
index 18e57ba3..5d85eaa2 100755
Binary files a/examples/ipfs_node/wasm/artifacts/ipfs_rpc.wasm and b/examples/ipfs_node/wasm/artifacts/ipfs_rpc.wasm differ
diff --git a/examples/ipfs_node/wasm/artifacts/wasm_modules/ipfs_node.wasm b/examples/ipfs_node/wasm/artifacts/wasm_modules/ipfs_node.wasm
index 63ee598e..8821a79b 100644
Binary files a/examples/ipfs_node/wasm/artifacts/wasm_modules/ipfs_node.wasm and b/examples/ipfs_node/wasm/artifacts/wasm_modules/ipfs_node.wasm differ
diff --git a/examples/ipfs_node/wasm/ipfs_node/src/main.rs b/examples/ipfs_node/wasm/ipfs_node/src/main.rs
index b4bc71bc..ad0c1a60 100644
--- a/examples/ipfs_node/wasm/ipfs_node/src/main.rs
+++ b/examples/ipfs_node/wasm/ipfs_node/src/main.rs
@@ -39,7 +39,7 @@ pub fn put(file_path: String) -> String {
     let timeout = std::env::var(TIMEOUT_ENV_NAME).unwrap_or_else(|_| "1s".to_string());
     let cmd = format!("add --timeout {} -Q {}", timeout, file_path);
 
-    call_ipfs(cmd)
+    ipfs(cmd)
 }
 
 /// Get file by provided hash from IPFS, saves it to a temporary file and returns a path to it.
@@ -55,7 +55,7 @@ pub fn get(hash: String) -> String {
         timeout, result_file_path, hash
     );
 
-    call_ipfs(cmd);
+    ipfs(cmd);
 
     RESULT_FILE_PATH.to_string()
 }
@@ -71,22 +71,9 @@ pub fn get_address() -> String {
     }
 }
 
-fn call_ipfs(cmd: String) -> String {
-    unsafe {
-        // TODO: better error handling
-        match ipfs(cmd.as_ptr() as _, cmd.len() as _) {
-            0 => String::from_raw_parts(
-                fluence::internal::get_result_ptr() as _,
-                fluence::internal::get_result_size(),
-                fluence::internal::get_result_size(),
-            ),
-            _ => "host ipfs call failed".to_string(),
-        }
-    }
-}
-
+#[fce]
 #[link(wasm_import_module = "host")]
 extern "C" {
-    /// Put a file to ipfs, returns ipfs hash of the file.
-    fn ipfs(ptr: i32, size: i32) -> i32;
+    /// Execute provided cmd as a parameters of ipfs cli, return result.
+    pub fn ipfs(cmd: String) -> String;
 }
diff --git a/fluence-faas/src/faas.rs b/fluence-faas/src/faas.rs
index a3d6de08..607d598f 100644
--- a/fluence-faas/src/faas.rs
+++ b/fluence-faas/src/faas.rs
@@ -106,7 +106,16 @@ impl FluenceFaaS {
     }
 
     /// Executes provided Wasm code in the internal environment (with access to module exports).
-    pub fn call_code(
+    pub fn call_code<S: AsRef<str>>(
+        &mut self,
+        wasm: &[u8],
+        func_name: S,
+        args: &[IValue],
+    ) -> Result<Vec<IValue>> {
+        self.call_code_(wasm, func_name.as_ref(), args)
+    }
+
+    pub fn call_code_(
         &mut self,
         wasm: &[u8],
         func_name: &str,
@@ -125,10 +134,10 @@ impl FluenceFaaS {
     }
 
     /// Call a specified function of loaded on a startup module by its name.
-    pub fn call_module(
+    pub fn call_module<MN: AsRef<str>, FN: AsRef<str>>(
         &mut self,
-        module_name: &str,
-        func_name: &str,
+        module_name: MN,
+        func_name: FN,
         args: &[IValue],
     ) -> Result<Vec<IValue>> {
         self.fce
diff --git a/fluence-faas/src/misc/imports.rs b/fluence-faas/src/misc/imports.rs
index 2e0c94bd..c5813cca 100644
--- a/fluence-faas/src/misc/imports.rs
+++ b/fluence-faas/src/misc/imports.rs
@@ -93,7 +93,7 @@ where
     };
 
     DynamicFunc::new(
-        std::sync::Arc::new(FuncSig::new(vec![Type::I32, Type::I32], vec![Type::I32])),
+        std::sync::Arc::new(FuncSig::new(vec![Type::I32, Type::I32], vec![])),
         func,
     )
 }
diff --git a/fluence-faas/src/misc/utils.rs b/fluence-faas/src/misc/utils.rs
index bf03c36f..dc9680f3 100644
--- a/fluence-faas/src/misc/utils.rs
+++ b/fluence-faas/src/misc/utils.rs
@@ -14,20 +14,19 @@
  * limitations under the License.
  */
 
-use wasmer_core::vm::Ctx;
-use crate::FaaSError;
 use super::config::ModuleConfig;
 
 use fce::FCEModuleConfig;
 
+use wasmer_core::backend::SigRegistry;
+use wasmer_core::module::ExportIndex;
+use wasmer_core::vm::Ctx;
 use wasmer_core::import::ImportObject;
-use wasmer_runtime::func;
 use wasmer_core::typed_func::WasmTypeList;
+use wasmer_runtime::func;
 use wasmer_runtime::Func;
 use wasmer_runtime::error::ResolveError;
-use wasmer_core::backend::SigRegistry;
 use wasmer_runtime::types::LocalOrImport;
-use wasmer_core::module::ExportIndex;
 
 use std::path::PathBuf;
 
@@ -103,7 +102,7 @@ where
 }
 
 /// Make FCE config based on parsed raw config.
-pub(crate) fn make_fce_config(config: Option<ModuleConfig>) -> Result<FCEModuleConfig, FaaSError> {
+pub(crate) fn make_fce_config(config: Option<ModuleConfig>) -> crate::Result<FCEModuleConfig> {
     use super::imports::create_host_import_func;
     use super::imports::log_utf8_string;
     use wasmer_core::import::Namespace;
diff --git a/tools/cli/src/args.rs b/tools/cli/src/args.rs
index 36cca3aa..c8eaa5f6 100644
--- a/tools/cli/src/args.rs
+++ b/tools/cli/src/args.rs
@@ -25,15 +25,15 @@ pub const IN_WASM_PATH: &str = "in-wasm-path";
 pub fn build<'a, 'b>() -> App<'a, 'b> {
     SubCommand::with_name("build")
         .about("build provided Rust project to Wasm")
-        .args(&[Arg::with_name(IN_WASM_PATH)
-            .takes_value(true)
-            .short("i")
-            .help("path to a Cargo.toml file")])
+        .setting(clap::AppSettings::TrailingVarArg)
+        .setting(clap::AppSettings::AllowLeadingHyphen)
+        .arg(Arg::from_usage("[optional]... 'cargo build arguments'").multiple(true))
 }
 
 pub fn show_wit<'a, 'b>() -> App<'a, 'b> {
     SubCommand::with_name("show")
         .about("show WIT in provided Wasm file")
+        .setting(clap::AppSettings::ArgRequiredElseHelp)
         .args(&[Arg::with_name(IN_WASM_PATH)
             .required(true)
             .takes_value(true)
diff --git a/tools/cli/src/build.rs b/tools/cli/src/build.rs
index 7300d4ba..9e1d4ee9 100644
--- a/tools/cli/src/build.rs
+++ b/tools/cli/src/build.rs
@@ -17,7 +17,6 @@
 use crate::Result;
 use crate::errors::CLIError;
 
-use std::path::PathBuf;
 use std::process::Command;
 
 #[derive(serde::Deserialize)]
@@ -29,15 +28,13 @@ enum DiagnosticMessage {
     RunWithArgs,
 }
 
-pub(crate) fn build(manifest_path: Option<PathBuf>) -> Result<()> {
+pub(crate) fn build(trailing_args: Vec<&str>) -> Result<()> {
     use std::io::Read;
 
     let mut cargo = Command::new("cargo");
     cargo.arg("build").arg("--target").arg("wasm32-wasi");
     cargo.arg("--message-format").arg("json-render-diagnostics");
-    if let Some(wasm_path) = manifest_path {
-        cargo.arg("--manifest-path").arg(wasm_path);
-    }
+    cargo.args(trailing_args);
 
     let mut process = cargo.stdout(std::process::Stdio::piped()).spawn()?;
 
diff --git a/tools/cli/src/main.rs b/tools/cli/src/main.rs
index e77dc56b..1f4ec738 100644
--- a/tools/cli/src/main.rs
+++ b/tools/cli/src/main.rs
@@ -29,27 +29,22 @@ mod args;
 mod build;
 mod errors;
 
-use clap::App;
-use clap::AppSettings;
-
 pub(crate) type Result<T> = std::result::Result<T, crate::errors::CLIError>;
 
 pub fn main() -> Result<()> {
-    let app = App::new("CLI tool for embedding WIT to provided Wasm file")
+    let app = clap::App::new("CLI tool for embedding WIT to provided Wasm file")
         .version(args::VERSION)
         .author(args::AUTHORS)
         .about(args::DESCRIPTION)
-        .setting(AppSettings::ArgRequiredElseHelp)
         .subcommand(args::build())
         .subcommand(args::show_wit());
+    let arg_matches = app.get_matches();
 
-    match app.get_matches().subcommand() {
-        ("build", Some(arg)) => {
-            let manifest_path = arg
-                .value_of(args::IN_WASM_PATH)
-                .map(std::path::PathBuf::from);
+    match arg_matches.subcommand() {
+        ("build", Some(args)) => {
+            let trailing_args: Vec<&str> = args.values_of("optional").unwrap_or_default().collect();
 
-            crate::build::build(manifest_path)
+            crate::build::build(trailing_args)
         }
         ("show", Some(arg)) => {
             let wasm_path = arg.value_of(args::IN_WASM_PATH).unwrap();