diff --git a/ui-repolist.c b/ui-repolist.c
index c23232c..2324273 100644
--- a/ui-repolist.c
+++ b/ui-repolist.c
@@ -6,6 +6,10 @@
  *   (see COPYING for full license text)
  */
 
+/* This is needed for strcasestr to be defined by <string.h> */
+#define _GNU_SOURCE 1
+#include <string.h>
+
 #include <time.h>
 
 #include "cgit.h"