diff --git a/diff.c b/diff.c
index 3c88c37908..e5b5f16fd0 100644
--- a/diff.c
+++ b/diff.c
@@ -3992,6 +3992,13 @@ static int reuse_worktree_file(struct index_state *istate,
 	if (!FAST_WORKING_DIRECTORY && !want_file && has_object_pack(oid))
 		return 0;
 
+	/*
+	 * If this path does not match our sparse-checkout definition,
+	 * then the file will not be in the working directory.
+	 */
+	if (!path_in_sparse_checkout(name, istate))
+		return 0;
+
 	/*
 	 * Similarly, if we'd have to convert the file contents anyway, that
 	 * makes the optimization not worthwhile.