diff --git a/dargs/dargs.py b/dargs/dargs.py
index f067b01..ed698db 100644
--- a/dargs/dargs.py
+++ b/dargs/dargs.py
@@ -898,6 +898,14 @@ def dummy_argument(self) -> Argument:
     def get_choice(self, argdict: dict, path: list[str] | None = None) -> Argument:
         if self.flag_name in argdict:
             tag = argdict[self.flag_name]
+            choices = [*self.choice_dict, *self.choice_alias]
+            if not isinstance(tag, str):
+                raise ArgumentTypeError(
+                    path,
+                    f"key `{self.flag_name}` gets wrong value type, requires <str> "
+                    f"but {type(tag).__name__} is given; "
+                    f"expected choices are <{'|'.join(choices)}>",
+                )
             if tag in self.choice_dict:
                 return self.choice_dict[tag]
             elif tag in self.choice_alias:
@@ -906,10 +914,7 @@ def get_choice(self, argdict: dict, path: list[str] | None = None) -> Argument:
                 raise ArgumentValueError(
                     path,
                     f"get invalid choice `{tag}` for flag key `{self.flag_name}`."
-                    + did_you_mean(
-                        tag,
-                        list(self.choice_dict.keys()) + list(self.choice_alias.keys()),
-                    ),
+                    + did_you_mean(tag, choices),
                 )
         elif self.optional:
             return self.choice_dict[self.default_tag]
@@ -934,7 +939,11 @@ def _convert_choice_alias(
     ) -> None:
         if self.flag_name in argdict:
             tag = argdict[self.flag_name]
-            if tag not in self.choice_dict and tag in self.choice_alias:
+            if (
+                isinstance(tag, str)
+                and tag not in self.choice_dict
+                and tag in self.choice_alias
+            ):
                 argdict[self.flag_name] = self.choice_alias[tag]
 
     # above are traversing part
diff --git a/tests/test_checker.py b/tests/test_checker.py
index 4486c7a..4143f36 100644
--- a/tests/test_checker.py
+++ b/tests/test_checker.py
@@ -165,6 +165,25 @@ def test_sub_repeat_dict(self) -> None:
         with self.assertRaises(ArgumentTypeError):
             ca.check(err_dict3)
 
+    def test_variant_choice_type(self) -> None:
+        ca = Argument(
+            "base",
+            dict,
+            sub_variants=[Variant("kind", [Argument("alpha", dict, alias=["a"])])],
+        )
+        for tag in ([], {}, 1, None):
+            with self.subTest(tag=tag):
+                with self.assertRaises(ArgumentTypeError) as cm:
+                    ca.normalize_value({"kind": tag})
+                self.assertEqual(cm.exception.path, "")
+                self.assertIn("requires <str>", str(cm.exception))
+                self.assertIn("expected choices are <alpha|a>", str(cm.exception))
+
+        self.assertEqual(ca.normalize_value({"kind": "a"}), {"kind": "alpha"})
+        with self.assertRaises(ArgumentValueError) as cm:
+            ca.normalize_value({"kind": "alpah"})
+        self.assertIn("Did you mean: alpha?", str(cm.exception))
+
     def test_sub_variants(self) -> None:
         ca = Argument(
             "base",