diff --git a/src/type.ts b/src/type.ts
index 4f2d6e61..97b28746 100644
--- a/src/type.ts
+++ b/src/type.ts
@@ -168,7 +168,7 @@ export function getTypeNameBySource(typeSource: Ast.TypeSource): string {
 export function getTypeBySource(typeSource: Ast.TypeSource, typeParams?: readonly Ast.TypeParam[]): Type {
 	if (typeSource.type === 'namedTypeSource') {
 		const typeParam = typeParams?.find((param) => param.name === typeSource.name);
-		if (typeParam != null) {
+		if (typeParam != null && typeSource.inner == null) {
 			return T_PARAM(typeParam.name);
 		}
 
diff --git a/test/types.ts b/test/types.ts
index d876e00a..e0e4b2e4 100644
--- a/test/types.ts
+++ b/test/types.ts
@@ -1,8 +1,8 @@
 import * as assert from 'assert';
-import { describe, test } from 'vitest';
+import { describe, expect, test } from 'vitest';
 import { utils } from '../src';
 import { NUM, STR, NULL, ARR, OBJ, BOOL, TRUE, FALSE, ERROR ,FN_NATIVE } from '../src/interpreter/value';
-import { AiScriptRuntimeError } from '../src/error';
+import { AiScriptRuntimeError, AiScriptSyntaxError } from '../src/error';
 import { exe, getMeta, eq } from './testutils';
 
 describe('function types', () => {
@@ -108,6 +108,12 @@ describe('generics', () => {
 			@f<>() {}
 			`));
 		});
+
+		test.concurrent('cannot have inner type', async () => {
+			await expect(() => exe(`
+			@f<T>(v: T<num>) {}
+			`)).rejects.toThrow(AiScriptSyntaxError);
+		});
 	});
 });
 
diff --git a/unreleased/fix-type-param-inner-type-is-allowed.md b/unreleased/fix-type-param-inner-type-is-allowed.md
new file mode 100644
index 00000000..5dc602d1
--- /dev/null
+++ b/unreleased/fix-type-param-inner-type-is-allowed.md
@@ -0,0 +1 @@
+- Fix: 型引数で定義された型に型引数を与えてもエラーが発生しない問題を修正