diff --git a/tests/hooks/plugin-hook-bootstrap-no-echo.test.js b/tests/hooks/plugin-hook-bootstrap-no-echo.test.js
index 3d9f1cb79..e896ec48b 100644
--- a/tests/hooks/plugin-hook-bootstrap-no-echo.test.js
+++ b/tests/hooks/plugin-hook-bootstrap-no-echo.test.js
@@ -277,8 +277,11 @@ if (
       );
     }
 
-    const mismatchedPrefix = Buffer.from(raw.subarray(0, 8 * 1024));
-    mismatchedPrefix[mismatchedPrefix.length - 1] ^= 1;
+    const mismatchLength = 8 * 1024;
+    const mismatchedPrefix = Buffer.concat([
+      raw.subarray(0, mismatchLength - 1),
+      Buffer.from([raw[mismatchLength - 1] ^ 1])
+    ]);
     assert.strictEqual(isRawPassthrough(raw, mismatchedPrefix), false);
   })
 )