diff --git a/include/lib/fex/lexer.h b/include/lib/fex/lexer.h
index b888e86b..9b22976d 100644
--- a/include/lib/fex/lexer.h
+++ b/include/lib/fex/lexer.h
@@ -1,6 +1,7 @@
 #ifndef INCLUDE_CORE_LEXER_H
 #define INCLUDE_CORE_LEXER_H
 
+#include <cstdint>
 #include <string>
 #include <vector>