diff --git a/CHANGELOG.md b/CHANGELOG.md
index fffdd1cf249..e1aac9e09e5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,4 @@
+- Revert enabling preferRest by default to avoid performance degradations for some users (#6520).
 - Fix blocking functions in the emulator when using multiple codebases (#6504).
 - Add force flag call-out for bypassing prompts (#6506).
 - Fixed an issue where the functions emulator did not respect the `--log-verbosity` flag (#2859).
diff --git a/src/functions/env.ts b/src/functions/env.ts
index 92cc4f19492..b640aff443e 100644
--- a/src/functions/env.ts
+++ b/src/functions/env.ts
@@ -410,6 +410,5 @@ export function loadFirebaseEnvs(
   return {
     FIREBASE_CONFIG: JSON.stringify(firebaseConfig),
     GCLOUD_PROJECT: projectId,
-    FIRESTORE_PREFER_REST: "true",
   };
 }