diff --git a/src/structs.h b/src/structs.h
index e581e43..6eb43f8 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -1127,8 +1127,13 @@
 #ifdef FEAT_NUM64
 /* Use 64-bit Number. */
 # ifdef WIN3264
+#  ifdef PROTO
+typedef long		    varnumber_T;
+typedef unsigned long	    uvarnumber_T;
+#  else
 typedef __int64		    varnumber_T;
 typedef unsigned __int64    uvarnumber_T;
+#  endif
 # elif defined(HAVE_STDINT_H)
 typedef int64_t		    varnumber_T;
 typedef uint64_t	    uvarnumber_T;