diff --git a/src/apps/acbunpack/acbunpack.cpp b/src/apps/acbunpack/acbunpack.cpp
index 678e413..d3199bf 100644
--- a/src/apps/acbunpack/acbunpack.cpp
+++ b/src/apps/acbunpack/acbunpack.cpp
@@ -10,6 +10,7 @@
 
 #else
 #include <sys/stat.h>
+#include <unistd.h>
 #endif
 
 #include "../../lib/cgss_api.h"