diff --git a/mrbgems/mruby-bin-mrbc/tools/mrbc/stub.c b/mrbgems/mruby-bin-mrbc/tools/mrbc/stub.c
index ba6a4bd1d..a0c982230 100644
--- a/mrbgems/mruby-bin-mrbc/tools/mrbc/stub.c
+++ b/mrbgems/mruby-bin-mrbc/tools/mrbc/stub.c
@@ -94,3 +94,11 @@ void mrb_gc_free_set(mrb_state *mrb, struct RBasic *obj)
   /* stub for mrbc */
 }
 #endif
+
+#ifdef MRB_USE_TASK_SCHEDULER
+void mrb_task_mark_all(mrb_state *mrb)
+{
+  /* stub for mrbc */
+  (void)mrb;
+}
+#endif
diff --git a/src/gc.c b/src/gc.c
index 286b32c3e..83f3f9c0d 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -29,8 +29,8 @@
 #endif
 
 #ifdef MRB_USE_TASK_SCHEDULER
-/* Weak stub for mrb_task_mark_all - actual implementation in task.c */
-void __attribute__((weak)) mrb_task_mark_all(mrb_state *mrb) { (void)mrb; }
+/* Forward declaration - actual implementation in task.c */
+void mrb_task_mark_all(mrb_state *mrb);
 #endif
 
 /*