1 files changed, 1 insertions, 0 deletions
diff --git a/rubyio.h b/rubyio.h
index 1df37b1501..979c6e607b 100644
--- a/rubyio.h
+++ b/rubyio.h
@@ -36,6 +36,7 @@ typedef struct OpenFile {
 #define GetOpenFile(obj,fp) rb_io_check_closed((fp) = RFILE(obj)->fptr)
 
 #define MakeOpenFile(obj, fp) do {\
+    RFILE(obj)->iv_tbl = 0;\
     fp = RFILE(obj)->fptr = ALLOC(OpenFile);\
     fp->f = fp->f2 = NULL;\
     fp->mode = 0;\