diff --git a/include/pocketpy/frame.h b/include/pocketpy/frame.h
index 90f90112..647d039d 100644
--- a/include/pocketpy/frame.h
+++ b/include/pocketpy/frame.h
@@ -122,6 +122,8 @@ struct Frame {
     void _gc_mark() const {
         PK_OBJ_MARK(_module);
         co->_gc_mark();
+        // Frame could be stored in a generator, so mark _callable for safety
+        if(_callable != nullptr) PK_OBJ_MARK(_callable);
     }
 };