1 files changed, 1 insertions, 0 deletions
diff --git a/src/undo.c b/src/undo.c
index 0903dbf708..87adf3f9bc 100644
--- a/src/undo.c
+++ b/src/undo.c
@@ -98,6 +98,7 @@
 #include "quickfix.h"
 #include "screen.h"
 #include "sha256.h"
+#include "os/os.h"
 
 static long get_undolevel(void);
 static void u_unch_branch(u_header_T *uhp);