diff --git a/src/driver/slbt_driver_ctx.c b/src/driver/slbt_driver_ctx.c
index 5f5f609..8a1b0ec 100644
--- a/src/driver/slbt_driver_ctx.c
+++ b/src/driver/slbt_driver_ctx.c
@@ -4,6 +4,10 @@
 /*  Released under the Standard MIT License; see COPYING.SLIBTOOL. */
 /*******************************************************************/
 
+#ifndef _POSIX_C_SOURCE
+#define _POSIX_C_SOURCE 200809L
+#endif
+
 #include <stdint.h>
 #include <unistd.h>
 #include <fcntl.h>