1 files changed, 1 insertions, 1 deletions
diff --git a/io.c b/io.c
index be5d479099..1b7cdc86f5 100644
--- a/io.c
+++ b/io.c
@@ -1091,7 +1091,7 @@ ruby_dup(int orig)
 static VALUE
 io_alloc(VALUE klass)
 {
-    NEWOBJ_OF(io, struct RFile, klass, T_FILE);
+    NEWOBJ_OF(io, struct RFile, klass, T_FILE, sizeof(struct RFile), 0);
 
     io->fptr = 0;