diff --git a/lib/std/Io/Writer.zig b/lib/std/Io/Writer.zig
index e4eb52d294ec7972b2059ada1fb9e15f313b3f6a..c5dd1f6bae8a7dce41a8ff26692e73fc43c65ba3 100644
--- a/lib/std/Io/Writer.zig
+++ b/lib/std/Io/Writer.zig
@@ -771,7 +771,7 @@ pub fn writeBytePreserve(w: *Writer, preserve: usize, byte: u8) Error!void {
         w.end += 1;
         return;
     }
-    try w.vtable.rebase(w, preserve, 1);
+    try w.vtable.rebase(w, preserve -| 1, 1);
     w.buffer[w.end] = byte;
     w.end += 1;
 }