1 files changed, 6 insertions, 1 deletions
diff --git a/gc.c b/gc.c
index 42525695e9..2a191ae90e 100644
--- a/gc.c
+++ b/gc.c
@@ -5734,13 +5734,18 @@ rb_copy_wb_protected_attribute(VALUE dest, VALUE obj)
 #if USE_RGENGC
     rb_objspace_t *objspace = &rb_objspace;
 
+    if (RGENGC_CHECK_MODE > 0 && RVALUE_WB_UNPROTECTED(dest)) {
+	rb_bug("rb_copy_wb_protected_attribute: dest should not be WB unprotected - %s",
+	       obj_info(dest));
+    }
+
     if (RVALUE_WB_UNPROTECTED(obj)) {
 	if (!RVALUE_OLD_P(dest)) {
 	    MARK_IN_BITMAP(GET_HEAP_WB_UNPROTECTED_BITS(dest), dest);
 	    RVALUE_AGE_RESET_RAW(dest);
 	}
 	else {
-	    RVALUE_DEMOTE(objspace, obj);
+	    RVALUE_DEMOTE(objspace, dest);
 	}
     }