diff --git a/environment.c b/environment.c
index ba9781b71..4b7ecab8b 100644
--- a/environment.c
+++ b/environment.c
@@ -9,6 +9,7 @@
  */
 #include "cache.h"
 #include "refs.h"
+#include "fmt-merge-msg.h"
 
 char git_default_email[MAX_GITNAME];
 char git_default_name[MAX_GITNAME];