diff --git a/pdoc/doc.py b/pdoc/doc.py
index 752cd178..a09cddb2 100644
--- a/pdoc/doc.py
+++ b/pdoc/doc.py
@@ -637,7 +637,7 @@ def _var_annotations(self) -> dict[str, type]:
                 for attr, unresolved_annotation in dynamic_annotations.items():
                     cls_annotations[attr] = unresolved_annotation
             cls_fullname = (
-                _safe_getattr(cls, "__module__", "") + "." + cls.__qualname__
+                (_safe_getattr(cls, "__module__", "") or "") + "." + cls.__qualname__
             ).lstrip(".")
 
             new_annotations = {