diff --git a/source/cd_linux.c b/source/cd_linux.c
index 6ae0b39..54db21c 100644
--- a/source/cd_linux.c
+++ b/source/cd_linux.c
@@ -31,6 +31,9 @@
 #endif
 
 #include <fcntl.h>
+#ifdef HAVE_UNISTD_H
+#include "unistd.h"
+#endif
 #ifdef HAVE_STRING_H
 #include <string.h>
 #endif