diff --git a/lib/inc/drogon/RateLimiter.h b/lib/inc/drogon/RateLimiter.h
index 6940321..2c5f039 100644
--- a/lib/inc/drogon/RateLimiter.h
+++ b/lib/inc/drogon/RateLimiter.h
@@ -3,6 +3,7 @@
 #include <memory>
 #include <chrono>
 #include <mutex>
+#include <string>
 
 namespace drogon
 {