diff --git a/tree-walk.c b/tree-walk.c
index 38b6556..59add24 100644
--- a/tree-walk.c
+++ b/tree-walk.c
@@ -5,6 +5,7 @@
 #include "gettext.h"
 #include "hex.h"
 #include "object-store.h"
+#include "trace2.h"
 #include "tree.h"
 #include "pathspec.h"
 #include "json-writer.h"