diff --git a/tools/build/binpatch.c b/tools/build/binpatch.c
index d85303e171..9c0a899a26 100644
--- a/tools/build/binpatch.c
+++ b/tools/build/binpatch.c
@@ -5,6 +5,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <assert.h>
+#include <unistd.h>
 
 static char buf[512];