diff --git a/src/eapol.c b/src/eapol.c
index ab77746f..372549c6 100644
--- a/src/eapol.c
+++ b/src/eapol.c
@@ -24,6 +24,7 @@
 #include <config.h>
 #endif
 
+#define _GNU_SOURCE
 #include <string.h>
 #include <alloca.h>
 #include <linux/if_ether.h>