diff --git a/tools/winebuild/build.h b/tools/winebuild/build.h
index 73da0c7..a74fe7f 100644
--- a/tools/winebuild/build.h
+++ b/tools/winebuild/build.h
@@ -73,7 +73,7 @@
 typedef struct
 {
     int  n_args;
-    char arg_types[17];
+    char arg_types[21];
 } ORD_FUNCTION;
 
 typedef struct