diff --git a/src/cpp/include/UTIL/CheckCollections.h b/src/cpp/include/UTIL/CheckCollections.h
index e7ae22d73..f15a374b8 100644
--- a/src/cpp/include/UTIL/CheckCollections.h
+++ b/src/cpp/include/UTIL/CheckCollections.h
@@ -3,6 +3,7 @@
 
 #include "lcio.h"
 
+#include <cstdint>
 #include <string>
 #include <unordered_map>
 #include <set>