diff --git a/src/OpenFOAM/primitives/strings/word/word.C b/src/OpenFOAM/primitives/strings/word/word.C
index 6465c41962..a1a66656d8 100644
--- a/src/OpenFOAM/primitives/strings/word/word.C
+++ b/src/OpenFOAM/primitives/strings/word/word.C
@@ -30,6 +30,7 @@ License
 #include "debug.H"
 #include <cctype>
 #include <sstream>
+#include <cstdint>
 
 // * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //