diff --git a/src/internal.hpp b/src/internal.hpp
index cbc5c9f..978848f 100644
--- a/src/internal.hpp
+++ b/src/internal.hpp
@@ -1,5 +1,6 @@
 #pragma once
 
+#include <cstdint>
 #include <cstddef>
 #include <iostream>
 #include <limits>
@@ -540,4 +541,4 @@ const uint64_t TETRAMER_TAB[4 * 4 * 4 * 4] = {
   10664720106027613972U
 };
 
-} // namespace nthash
\ No newline at end of file
+} // namespace nthash