diff --git a/crates/red_knot_python_semantic/src/types.rs b/crates/red_knot_python_semantic/src/types.rs
index 89623d383a47c9..a5bb0df88b90b3 100644
--- a/crates/red_knot_python_semantic/src/types.rs
+++ b/crates/red_knot_python_semantic/src/types.rs
@@ -523,11 +523,6 @@ impl<'db> Type<'db> {
                 .elements(db)
                 .iter()
                 .any(|&elem_ty| ty.is_subtype_of(db, elem_ty)),
-            (Type::Instance(self_class), Type::Instance(target_class))
-                if self_class.is_known(db, KnownClass::NoneType) =>
-            {
-                target_class.is_known(db, KnownClass::NoneType)
-            }
             (Type::Instance(self_class), Type::Instance(target_class)) => {
                 self_class.is_subclass_of(db, target_class)
             }
@@ -1848,7 +1843,10 @@ impl<'db> ClassType<'db> {
 
     pub fn is_subclass_of(self, db: &'db dyn Db, other: ClassType) -> bool {
         // TODO: we need to iterate over the *MRO* here, not the bases
+        // Note: the other == self check tests for equality of salsa IDs, but not for
+        // actual equality of the classes.
         (other == self)
+            || (self.known(db) == other.known(db))
             || self.bases(db).any(|base| match base {
                 Type::ClassLiteral(base_class) => base_class == other,
                 // `is_subclass_of` is checking the subtype relation, in which gradual types do not