diff --git a/flaml/tune/searcher/flow2.py b/flaml/tune/searcher/flow2.py
index 035e3d8688..7c0f48472f 100644
--- a/flaml/tune/searcher/flow2.py
+++ b/flaml/tune/searcher/flow2.py
@@ -746,10 +746,13 @@ def reach(self, other: Searcher) -> bool:
             # unordered cat choice is hard to reach by chance
             if config1[key] != config2.get(key):
                 return False
-        delta = np.array(
-            [
-                incumbent1[key] - incumbent2.get(key, np.inf)
-                for key in self._tunable_keys
-            ]
-        )
+        try:
+            delta = np.array(
+                [
+                    incumbent1[key] - incumbent2.get(key, np.inf)
+                    for key in self._tunable_keys
+                ]
+            )
+        except TypeError:
+            return False
         return np.linalg.norm(delta) <= self.step
diff --git a/test/automl/test_classification.py b/test/automl/test_classification.py
index adb3081662..aab0370861 100644
--- a/test/automl/test_classification.py
+++ b/test/automl/test_classification.py
@@ -408,6 +408,14 @@ def test_sparse_matrix_lr(self):
         print(automl_experiment.best_iteration)
         print(automl_experiment.best_estimator)
 
+    def test_reach(self):
+        search_space = {
+            "params": tune.choice(
+                [{"param": "None"}, {"param": tune.qrandint(10, 100, 10)}]
+            ),
+        }
+        return search_space
+
 
 if __name__ == "__main__":
     test = TestClassification()