diff --git a/sys/net/application_layer/sock_dns/dns.c b/sys/net/application_layer/sock_dns/dns.c
index 3a8fa6ea3d..664e52af75 100644
--- a/sys/net/application_layer/sock_dns/dns.c
+++ b/sys/net/application_layer/sock_dns/dns.c
@@ -16,6 +16,7 @@
  */
 
 #include <errno.h>
+#include <string.h>
 
 #include "net/dns.h"
 #include "net/dns/msg.h"