@@ -107,7 +107,7 @@ Maybe<FunctionSignature> ParseFunctionSignature(Environment* env,
     }
 
     if (!return_type_val->IsString()) {
-      THROW_ERR_INVALID_ARG_VALUE(
+      THROW_ERR_INVALID_ARG_TYPE(
           env, "Return value type of function %s must be a string", name);
       return {};
     }
@@ -132,7 +132,7 @@ Maybe<FunctionSignature> ParseFunctionSignature(Environment* env,
     }
 
     if (!arguments_val->IsArray()) {
-      THROW_ERR_INVALID_ARG_VALUE(
+      THROW_ERR_INVALID_ARG_TYPE(
           env, "Arguments list of function %s must be an array", name);
       return {};
     }
@@ -148,7 +148,7 @@ Maybe<FunctionSignature> ParseFunctionSignature(Environment* env,
       }
 
       if (!arg->IsString()) {
-        THROW_ERR_INVALID_ARG_VALUE(
+        THROW_ERR_INVALID_ARG_TYPE(
             env, "Argument %u of function %s must be a string", i, name);
         return {};
       }
 
@@ -432,6 +432,24 @@ test('dynamic library APIs validate failures and bad signatures', () => {
       lib.getFunction('add_i32', { return: 'i32', arguments: ['i32\0bad'] });
     }, /Argument 0 of function add_i32 must not contain null bytes/);
 
+    assert.throws(() => {
+      lib.getFunction('add_i32', { return: 1, arguments: [] });
+    }, {
+      code: 'ERR_INVALID_ARG_TYPE',
+    });
+
+    assert.throws(() => {
+      lib.getFunction('add_i32', { return: 'i32', arguments: 'i32' });
+    }, {
+      code: 'ERR_INVALID_ARG_TYPE',
+    });
+
+    assert.throws(() => {
+      lib.getFunction('add_i32', { return: 'i32', arguments: [1] });
+    }, {
+      code: 'ERR_INVALID_ARG_TYPE',
+    });
+
     assert.throws(() => {
       lib.getFunctions('not an object');
     }, {
Original file line number	Diff line number	Diff line change
`@@ -107,7 +107,7 @@ Maybe<FunctionSignature> ParseFunctionSignature(Environment* env,`
`107`	`107`	`}`
`108`	`108`
`109`	`109`	`if (!return_type_val->IsString()) {`
`110`		`- THROW_ERR_INVALID_ARG_VALUE(`
	`110`	`+ THROW_ERR_INVALID_ARG_TYPE(`
`111`	`111`	`env, "Return value type of function %s must be a string", name);`
`112`	`112`	`return {};`
`113`	`113`	`}`
`@@ -132,7 +132,7 @@ Maybe<FunctionSignature> ParseFunctionSignature(Environment* env,`
`132`	`132`	`}`
`133`	`133`
`134`	`134`	`if (!arguments_val->IsArray()) {`
`135`		`- THROW_ERR_INVALID_ARG_VALUE(`
	`135`	`+ THROW_ERR_INVALID_ARG_TYPE(`
`136`	`136`	`env, "Arguments list of function %s must be an array", name);`
`137`	`137`	`return {};`
`138`	`138`	`}`
`@@ -148,7 +148,7 @@ Maybe<FunctionSignature> ParseFunctionSignature(Environment* env,`
`148`	`148`	`}`
`149`	`149`
`150`	`150`	`if (!arg->IsString()) {`
`151`		`- THROW_ERR_INVALID_ARG_VALUE(`
	`151`	`+ THROW_ERR_INVALID_ARG_TYPE(`
`152`	`152`	`env, "Argument %u of function %s must be a string", i, name);`
`153`	`153`	`return {};`
`154`	`154`	`}`