diff --git a/src/joserfc/_keys.py b/src/joserfc/_keys.py
index e33ab7e..10427f3 100644
--- a/src/joserfc/_keys.py
+++ b/src/joserfc/_keys.py
@@ -124,7 +124,8 @@ def __bool__(self) -> bool:
         return bool(self.keys)
 
     def __eq__(self, other: t.Any) -> bool:
-        assert isinstance(other, KeySet)
+        if not isinstance(other, KeySet):
+            return NotImplemented
         return self.keys == other.keys
 
     def as_dict(self, private: bool = False, **params: t.Any) -> KeySetSerialization:
diff --git a/tests/jwk/test_jwk_set.py b/tests/jwk/test_jwk_set.py
index 06c4bbc..c4b90a7 100644
--- a/tests/jwk/test_jwk_set.py
+++ b/tests/jwk/test_jwk_set.py
@@ -103,3 +103,16 @@ def test_key_eq_with_new_keys(self):
         key_set2 = KeySet([RSAKey.import_key(k.as_dict(private=True)) for k in key_set1])
         self.assertIsNot(key_set1, key_set2)
         self.assertEqual(key_set1, key_set2)
+
+    def test_key_set_eq_with_unrelated_type(self):
+        key_set = KeySet.generate_key_set("oct", 8, count=1)
+        self.assertFalse(key_set == "foo")
+        self.assertNotEqual(key_set, "foo")
+
+    def test_key_set_eq_uses_reflected_comparison(self):
+        class EqualToKeySet:
+            def __eq__(self, other):
+                return isinstance(other, KeySet)
+
+        key_set = KeySet.generate_key_set("oct", 8, count=1)
+        self.assertTrue(key_set == EqualToKeySet())