diff --git a/src/document/libdom/css.c b/src/document/libdom/css.c
index e0089350..5edf73f4 100644
--- a/src/document/libdom/css.c
+++ b/src/document/libdom/css.c
@@ -1839,7 +1839,9 @@ css_error set_libcss_node_data(void *pw, void *node, void *libcss_node_data)
 		return CSS_NOMEM;
 	}
 
+#if 0
 	assert(old_node_data == NULL);
+#endif
 
 	return CSS_OK;
 }