diff --git a/uncrustify/src/uncrustify.cpp b/uncrustify/src/uncrustify.cpp
index c65a7ac..3b09d63 100644
--- a/uncrustify/src/uncrustify.cpp
+++ b/uncrustify/src/uncrustify.cpp
@@ -8,6 +8,8 @@
 #define DEFINE_PCF_NAMES
 #define DEFINE_CHAR_TABLE
 
+#include <unistd.h>
+
 #include "uncrustify_version.h"
 #include "uncrustify_types.h"
 #include "char_table.h"