diff --git a/src/buffer.c b/src/buffer.c
index e156991e6..3c7f6ccb4 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -75,7 +75,7 @@ int buffer_replace2(struct buffer *b, char *pos, char *end, const char *str, int
 
 	delta = len - (end - pos);
 
-	if (bi_end(b) + delta >= b->data + b->size)
+	if (bi_end(b) + delta > b->data + b->size)
 		return 0;  /* no space left */
 
 	if (buffer_not_empty(b) &&