diff --git a/src/modems/hayes.c b/src/modems/hayes.c
index d492eb3..87c6cb1 100644
--- a/src/modems/hayes.c
+++ b/src/modems/hayes.c
@@ -36,6 +36,7 @@
 
 
 #ifdef __linux__
+# define _XOPEN_SOURCE
 # include <sys/file.h>
 #endif
 #include <sys/stat.h>