diff --git a/conf/cf-lex.l b/conf/cf-lex.l
index ddfe8c77..a43f9eb9 100644
--- a/conf/cf-lex.l
+++ b/conf/cf-lex.l
@@ -30,6 +30,7 @@
 #include <errno.h>
 #include <stdlib.h>
 #include <stdarg.h>
+#include <unistd.h>
 
 #define PARSER 1