diff --git a/aiohttp_security/api.py b/aiohttp_security/api.py
index ea184296..7ab241d9 100644
--- a/aiohttp_security/api.py
+++ b/aiohttp_security/api.py
@@ -64,10 +64,14 @@ async def authorized_userid(request: web.Request) -> Optional[str]:
     return user_id
 
 
-async def permits(request: web.Request, permission: Union[str, enum.Enum],
-                  context: Any = None) -> bool:
+def _validate_permission(permission: Union[str, enum.Enum]) -> None:
     if not permission or not isinstance(permission, (str, enum.Enum)):
         raise ValueError("Permission should be a str or enum value.")
+
+
+async def permits(request: web.Request, permission: Union[str, enum.Enum],
+                  context: Any = None) -> bool:
+    _validate_permission(permission)
     identity_policy: _AIP = request.config_dict.get(IDENTITY_KEY)
     autz_policy: _AAP = request.config_dict.get(AUTZ_KEY)
     if identity_policy is None or autz_policy is None:
@@ -104,13 +108,14 @@ async def check_authorized(request: web.Request) -> str:
 
 async def check_permission(request: web.Request, permission: Union[str, enum.Enum],
                            context: Any = None) -> None:
-    """Checker that passes only to authoraised users with given permission.
+    """Checker that passes only to authorized users with given permission.
 
     If user is not authorized - raises HTTPUnauthorized,
     if user is authorized and does not have permission -
     raises HTTPForbidden.
     """
 
+    _validate_permission(permission)
     await check_authorized(request)
     allowed = await permits(request, permission, context)
     if not allowed:
diff --git a/tests/test_no_auth.py b/tests/test_no_auth.py
index 9611a080..677623f2 100644
--- a/tests/test_no_auth.py
+++ b/tests/test_no_auth.py
@@ -1,6 +1,7 @@
+import pytest
 from aiohttp import web
 
-from aiohttp_security import authorized_userid, permits
+from aiohttp_security import authorized_userid, check_permission, permits
 
 
 async def test_authorized_userid(aiohttp_client):
@@ -33,3 +34,17 @@ async def check(request):
     client = await aiohttp_client(app)
     resp = await client.get('/')
     assert 200 == resp.status
+
+
+async def test_check_permission_rejects_invalid_value(aiohttp_client):
+
+    async def check(request):
+        with pytest.raises(ValueError):
+            await check_permission(request, None)  # type: ignore[arg-type]
+        return web.Response()
+
+    app = web.Application()
+    app.router.add_route('GET', '/', check)
+    client = await aiohttp_client(app)
+    resp = await client.get('/')
+    assert 200 == resp.status