diff --git a/build.rs b/build.rs
index e3d7ecace..c1b84739b 100644
--- a/build.rs
+++ b/build.rs
@@ -64,8 +64,12 @@ fn main() -> anyhow::Result<()> {
     };
     let backends = vec!["singlepass", "cranelift", "llvm"];
     with_backends(&mut spectests, &backends, |mut spectests| {
-        with_test_module(&mut spectests, "spec", |spectests| {
+        with_test_module(&mut spectests, "spec", |mut spectests| {
             let _spec_tests = test_directory(spectests, "tests/spectests", wast_processor)?;
+            with_test_module(&mut spectests, "custom", |spectests| {
+                let _spec_tests = test_directory(spectests, "tests/custom", wast_processor)?;
+                Ok(())
+            })?;
             Ok(())
         })?;
         Ok(())
diff --git a/tests/custom/nan-canonicalization.wast b/tests/custom/nan-canonicalization.wast
index 2e80ab39a..2df42add9 100644
--- a/tests/custom/nan-canonicalization.wast
+++ b/tests/custom/nan-canonicalization.wast
@@ -79,10 +79,10 @@
     (i32.reinterpret_f32 (call $nan-canonicalization-f32-func-call-target (f32.add (f32.reinterpret_i32 (get_local 0)) (f32.const 0))))
   )
   (func (export "nan-canonicalization-f32-func-call-indirect") (param i32) (result i32)
-    (i32.reinterpret_f32 (call_indirect (type $f32-id) (f32.reinterpret_i32 (get_local 0)) (i32.const 1)))
+    (i32.reinterpret_f32 (call_indirect (type $f32-id) (f32.reinterpret_i32 (get_local 0)) (i32.const 0)))
   )
   (func (export "nan-canonicalization-f32-func-call-indirect-cncl") (param i32) (result i32)
-    (i32.reinterpret_f32 (call_indirect (type $f32-id) (f32.add (f32.reinterpret_i32 (get_local 0)) (f32.const 0)) (i32.const 1)))
+    (i32.reinterpret_f32 (call_indirect (type $f32-id) (f32.add (f32.reinterpret_i32 (get_local 0)) (f32.const 0)) (i32.const 0)))
   )
 
   (func (export "nan-canonicalization-f64-add") (param i64) (result i64)
@@ -146,10 +146,10 @@
     (i64.reinterpret_f64 (call $nan-canonicalization-f64-func-call-target (f64.add (f64.reinterpret_i64 (get_local 0)) (f64.const 0))))
   )
   (func (export "nan-canonicalization-f64-func-call-indirect") (param i64) (result i64)
-    (i64.reinterpret_f64 (call_indirect (type $f64-id) (f64.reinterpret_i64 (get_local 0)) (i32.const 2)))
+    (i64.reinterpret_f64 (call_indirect (type $f64-id) (f64.reinterpret_i64 (get_local 0)) (i32.const 1)))
   )
   (func (export "nan-canonicalization-f64-func-call-indirect-cncl") (param i64) (result i64)
-    (i64.reinterpret_f64 (call_indirect (type $f64-id) (f64.add (f64.reinterpret_i64 (get_local 0)) (f64.const 0)) (i32.const 2)))
+    (i64.reinterpret_f64 (call_indirect (type $f64-id) (f64.add (f64.reinterpret_i64 (get_local 0)) (f64.const 0)) (i32.const 1)))
   )
 )
 
@@ -191,4 +191,4 @@
 (assert_return (invoke "nan-canonicalization-f64-func-call" (i64.const 0x7ff8000000000001)) (i64.const 0x7ff8000000000001))
 (assert_return (invoke "nan-canonicalization-f64-func-call-cncl" (i64.const 0x7ff8000000000001)) (i64.const 0x7ff8000000000000))
 (assert_return (invoke "nan-canonicalization-f64-func-call-indirect" (i64.const 0x7ff8000000000001)) (i64.const 0x7ff8000000000001))
-(assert_return (invoke "nan-canonicalization-f64-func-call-indirect-cncl" (i64.const 0x7ff8000000000001)) (i64.const 0x7ff8000000000000))
+(assert_return (invoke "nan-canonicalization-f64-func-call-indirect-cncl" (i64.const 0x7ff8000000000001)) (i64.const 0x7ff8000000000000))
\ No newline at end of file
diff --git a/tests/custom/stack-overflow.wast b/tests/custom/stack-overflow.wast
index 5ac245b88..5b9c78f5f 100644
--- a/tests/custom/stack-overflow.wast
+++ b/tests/custom/stack-overflow.wast
@@ -7,4 +7,4 @@
       (export "stack-overflow" (func 0))
       (elem (;0;) (i32.const 0) 0))
 
-(assert_exhaustion (invoke "stack-overflow"))
+(assert_exhaustion (invoke "stack-overflow") "stack overflow")