diff --git a/builtin/commit.c b/builtin/commit.c
index e1af9b1..cb73857 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -256,8 +256,10 @@
 		;
 	m = xcalloc(1, i);
 
-	if (with_tree)
-		overlay_tree_on_cache(with_tree, prefix);
+	if (with_tree) {
+		const char *max_prefix = pathspec_prefix(prefix, pattern);
+		overlay_tree_on_cache(with_tree, max_prefix);
+	}
 
 	for (i = 0; i < active_nr; i++) {
 		struct cache_entry *ce = active_cache[i];