diff --git a/src/llua.c b/src/llua.c
index 7371ec50..8f1df3c6 100644
--- a/src/llua.c
+++ b/src/llua.c
@@ -26,6 +26,8 @@
 #include "logging.h"
 #include "build.h"
 
+#include <ctype.h>
+
 #ifdef LUA_EXTRAS
 #include <tolua++.h>
 #endif /* LUA_EXTRAS */