diff --git a/toolkit/components/url-classifier/tests/mochitest/test_fastblock_bug1477046.html b/toolkit/components/url-classifier/tests/mochitest/test_fastblock_bug1477046.html
index 97c59c039468..ef7a2d8e0e9d 100644
--- a/toolkit/components/url-classifier/tests/mochitest/test_fastblock_bug1477046.html
+++ b/toolkit/components/url-classifier/tests/mochitest/test_fastblock_bug1477046.html
@@ -127,6 +127,7 @@ async function setupTest() {
   await SpecialPowers.pushPrefEnv({ "set": [
     ["browser.contentblocking.enabled", true],
     ["browser.fastblock.enabled", true],
+    ["browser.fastblock.limit", 0],
     ["browser.fastblock.timeout", 5000],
     ["network.http.tailing.enabled", true],
     ["privacy.trackingprotection.enabled", false],