diff --git a/confection/__init__.py b/confection/__init__.py
index 9c6922c..23d0672 100644
--- a/confection/__init__.py
+++ b/confection/__init__.py
@@ -960,7 +960,7 @@ def _update_from_parsed(
                 filled[key] = value
             if key not in final:
                 final[key] = value
-            if isinstance(value, dict):
+            if isinstance(value, dict) and isinstance(final[key], dict):
                 filled[key], final[key] = cls._update_from_parsed(
                     value, filled[key], final[key]
                 )
diff --git a/confection/tests/test_config.py b/confection/tests/test_config.py
index 5873eb2..662462c 100644
--- a/confection/tests/test_config.py
+++ b/confection/tests/test_config.py
@@ -1431,3 +1431,29 @@ def test_parse_strings_interpretable_as_ints():
     )
     assert cfg["a"]["foo"] == [3, "003", "y"]
     assert cfg["b"]["bar"] == 3
+
+
+def test_dict_casting():
+    class CastStrAsDict:
+        @classmethod
+        def validate(cls, value):
+            if isinstance(value, str):
+                return {value: True}
+            return value
+
+        @classmethod
+        def __get_validators__(cls):
+            yield cls.validate
+
+    class SectionSchema(BaseModel):
+        key: CastStrAsDict
+
+    class MainSchema(BaseModel):
+        section: SectionSchema
+
+    cfg = Config().from_str("""
+    [section]
+    key = 1
+    """)
+
+    assert my_registry.fill(cfg, schema=MainSchema) == {'section': {'key': 1}}