diff --git a/client/command.c b/client/command.c
index 78872d90..bdc0b9f8 100644
--- a/client/command.c
+++ b/client/command.c
@@ -24,7 +24,9 @@
 #include <config.h>
 #endif
 
+#define _GNU_SOURCE
 #include <stdio.h>
+#include <string.h>
 #include <ell/ell.h>
 #include <readline/readline.h>
 
diff --git a/client/display.c b/client/display.c
index 1ed4ff56..9528b9d7 100644
--- a/client/display.c
+++ b/client/display.c
@@ -24,6 +24,7 @@
 #include <config.h>
 #endif
 
+#define _GNU_SOURCE
 #include <stdio.h>
 #include <signal.h>