1 files changed, 2 insertions, 0 deletions
diff --git a/io.c b/io.c
index b03dac5e94..5055b29fdc 100644
--- a/io.c
+++ b/io.c
@@ -6346,6 +6346,8 @@ Init_IO(void)
 #endif
 #ifdef O_BINARY
     rb_file_const("BINARY", INT2FIX(O_BINARY));
+#else
+    rb_file_const("BINARY", INT2FIX(0));
 #endif
 #ifdef O_SYNC
     rb_file_const("SYNC", INT2FIX(O_SYNC));