diff --git a/headers/modsecurity/rules_set.h b/headers/modsecurity/rules_set.h
index e1574594d4..460202dc07 100644
--- a/headers/modsecurity/rules_set.h
+++ b/headers/modsecurity/rules_set.h
@@ -22,6 +22,7 @@
 #include <string>
 #include <vector>
 #include <list>
+#include <cstdint>
 #endif