diff --git a/stage2/High_level_prototypes/lisp.h b/stage2/High_level_prototypes/lisp.h
index 7f9c712..f52dd15 100644
--- a/stage2/High_level_prototypes/lisp.h
+++ b/stage2/High_level_prototypes/lisp.h
@@ -20,6 +20,7 @@
 #include <stdarg.h>
 #include <string.h>
 #include <ctype.h>
+#include <stdint.h>
 
 enum otype
 {