diff --git a/src/vim9class.c b/src/vim9class.c
index 062de8f..734967a 100644
--- a/src/vim9class.c
+++ b/src/vim9class.c
@@ -1025,7 +1025,9 @@
 	    if (*fup == NULL)
 		goto cleanup;
 
-	    mch_memmove(*fup, gap->ga_data, sizeof(ufunc_T *) * gap->ga_len);
+	    if (gap->ga_len != 0)
+		mch_memmove(*fup, gap->ga_data,
+					      sizeof(ufunc_T *) * gap->ga_len);
 	    vim_free(gap->ga_data);
 	    if (loop == 1)
 		cl->class_class_function_count_child = gap->ga_len;