diff --git a/src/memline.c b/src/memline.c
index 8cd9b80..a1c07a9 100644
--- a/src/memline.c
+++ b/src/memline.c
@@ -3834,7 +3834,8 @@
 					(buf->b_ml.ml_stack_size + STACK_INCR));
 	if (newstack == NULL)
 	    return -1;
-	mch_memmove(newstack, buf->b_ml.ml_stack,
+	if (top > 0)
+	    mch_memmove(newstack, buf->b_ml.ml_stack,
 					     (size_t)top * sizeof(infoptr_T));
 	vim_free(buf->b_ml.ml_stack);
 	buf->b_ml.ml_stack = newstack;