diff --git a/tests/unit/plugins/relay/api/test-relay-api-msg.cpp b/tests/unit/plugins/relay/api/test-relay-api-msg.cpp
index d29c3b582..7ebf3ac95 100644
--- a/tests/unit/plugins/relay/api/test-relay-api-msg.cpp
+++ b/tests/unit/plugins/relay/api/test-relay-api-msg.cpp
@@ -27,6 +27,7 @@
 
 extern "C"
 {
+#include <string.h>
 #include <time.h>
 #include <sys/time.h>
 #include <cjson/cJSON.h>