diff --git a/monitor/display.c b/monitor/display.c
index 2090b859..9b73f0cc 100644
--- a/monitor/display.c
+++ b/monitor/display.c
@@ -24,6 +24,7 @@
 #include <config.h>
 #endif
 
+#define _GNU_SOURCE
 #include <stdio.h>
 #include <errno.h>
 #include <unistd.h>
diff --git a/monitor/main.c b/monitor/main.c
index 72dd74c6..594eb938 100644
--- a/monitor/main.c
+++ b/monitor/main.c
@@ -24,10 +24,12 @@
 #include <config.h>
 #endif
 
+#define _GNU_SOURCE
 #include <stdio.h>
 #include <errno.h>
 #include <ctype.h>
 #include <stdlib.h>
+#include <string.h>
 #include <getopt.h>
 #include <signal.h>
 #include <sys/socket.h>
diff --git a/monitor/nlmon.c b/monitor/nlmon.c
index c83a65a1..94f2be3a 100644
--- a/monitor/nlmon.c
+++ b/monitor/nlmon.c
@@ -24,6 +24,7 @@
 #include <config.h>
 #endif
 
+#define _GNU_SOURCE
 #include <stdio.h>
 #include <errno.h>
 #include <ctype.h>
diff --git a/monitor/pcap.c b/monitor/pcap.c
index aae0956b..54ad9f55 100644
--- a/monitor/pcap.c
+++ b/monitor/pcap.c
@@ -24,11 +24,13 @@
 #include <config.h>
 #endif
 
+#define _GNU_SOURCE
 #include <stdio.h>
 #include <fcntl.h>
 #include <unistd.h>
 #include <stdlib.h>
 #include <sys/uio.h>
+#include <sys/types.h>
 #include <ell/ell.h>
 
 #include "monitor/pcap.h"