diff --git a/library/modules/Creatures.cpp b/library/modules/Creatures.cpp
index daa31ead9..7ef0f6a08 100644
--- a/library/modules/Creatures.cpp
+++ b/library/modules/Creatures.cpp
@@ -24,6 +24,7 @@ distribution.
 
 #include "Internal.h"
 
+#include <stddef.h>
 #include <string>
 #include <vector>
 #include <map>