diff --git a/diff.c b/diff.c
index 99744354a7..6e6f2a765c 100644
--- a/diff.c
+++ b/diff.c
@@ -1223,7 +1223,7 @@ static int reuse_worktree_file(const char *name, const unsigned char *sha1, int
 	 * objects however would tend to be slower as they need
 	 * to be individually opened and inflated.
 	 */
-	if (FAST_WORKING_DIRECTORY && !want_file && has_sha1_pack(sha1, NULL))
+	if (!FAST_WORKING_DIRECTORY && !want_file && has_sha1_pack(sha1, NULL))
 		return 0;
 
 	len = strlen(name);