diff --git a/apischema/json_schema/schema.py b/apischema/json_schema/schema.py
index 3c327918..ac1aeef7 100644
--- a/apischema/json_schema/schema.py
+++ b/apischema/json_schema/schema.py
@@ -217,8 +217,8 @@ def mapping(
         with context_setter(self):
             self._ignore_first_ref = True
             key = self.visit(key_type)
-        if key["type"] != JsonType.STRING:
-            raise ValueError("Mapping types must string-convertible key")
+        if "type" not in key or key["type"] != JsonType.STRING:
+            raise ValueError("Mapping types must have string-convertible keys")
         value = self.visit(value_type)
         if "pattern" in key:
             return json_schema(
diff --git a/tests/integration/test_deserialize_with_coercion.py b/tests/integration/test_deserialize_with_coercion.py
index 0eea512f..61c954a3 100644
--- a/tests/integration/test_deserialize_with_coercion.py
+++ b/tests/integration/test_deserialize_with_coercion.py
@@ -23,11 +23,7 @@ def test_coerce_json():
     key = "test"
     value = 2
     ret = deserialize(
-        MyClass,
-        {
-            "my_property": f'{{"{key}": {value}}}',
-        },
-        coerce=_coerce_json,
+        MyClass, {"my_property": f'{{"{key}": {value}}}'}, coerce=_coerce_json
     )
     assert isinstance(ret, MyClass)
     assert isinstance(ret.my_property, dict) and ret.my_property[key] == value
diff --git a/tests/integration/test_typed_dict.py b/tests/integration/test_dict.py
similarity index 81%
rename from tests/integration/test_typed_dict.py
rename to tests/integration/test_dict.py
index 76fa6b48..6d1a3791 100644
--- a/tests/integration/test_typed_dict.py
+++ b/tests/integration/test_dict.py
@@ -1,4 +1,5 @@
 from datetime import date
+from typing import Any, Dict, Mapping
 
 import pytest
 
@@ -8,6 +9,20 @@
 from apischema.typing import Annotated, TypedDict
 
 
+class MyDict(dict):
+    pass
+
+
+@pytest.mark.parametrize(
+    "tp", [dict, Dict[int, Any], pytest.param(MyDict, marks=pytest.mark.xfail), Mapping]
+)
+def test_dict(tp):
+    with pytest.raises(ValueError, match="string-convertible keys"):
+        deserialization_schema(tp)
+    with pytest.raises(ValueError, match="string-convertible keys"):
+        serialization_schema(tp)
+
+
 class TD1(TypedDict, total=False):
     key1: str