diff --git a/ext/robin_hood.h b/ext/robin_hood.h
index a8f3a78..1c1b1d8 100644
--- a/ext/robin_hood.h
+++ b/ext/robin_hood.h
@@ -41,6 +41,7 @@

 #include <algorithm>
 #include <cstdlib>
+#include <cstdint>
 #include <cstring>
 #include <functional>
 #include <memory> // only to support hash of smart pointers