--- a/modules/libpref/Preferences.cpp
+++ b/modules/libpref/Preferences.cpp
@@ -3893,19 +3893,31 @@ Preferences::InitInitialObjects()
   // We only want extended data from pre-release channels due to size. We
   // also want it to be recorded for local developer builds (non-official builds
   // on the "default" channel).
   bool developerBuild = false;
 #ifndef MOZILLA_OFFICIAL
   developerBuild = !strcmp(NS_STRINGIFY(MOZ_UPDATE_CHANNEL), "default");
 #endif
 
+  // Release Candidate builds are builds that think they are release builds, but
+  // are shipped to beta users. We still need extended data from these users.
+  bool releaseCandidateOnBeta = false;
+  if (!strcmp(NS_STRINGIFY(MOZ_UPDATE_CHANNEL), "release")) {
+    nsAutoCString updateChannelPrefValue;
+    Preferences::GetCString(kChannelPref, updateChannelPrefValue,
+                            PrefValueKind::Default);
+    releaseCandidateOnBeta = updateChannelPrefValue.EqualsLiteral("beta");
+  }
+
   if (!strcmp(NS_STRINGIFY(MOZ_UPDATE_CHANNEL), "nightly") ||
       !strcmp(NS_STRINGIFY(MOZ_UPDATE_CHANNEL), "aurora") ||
-      !strcmp(NS_STRINGIFY(MOZ_UPDATE_CHANNEL), "beta") || developerBuild) {
+      !strcmp(NS_STRINGIFY(MOZ_UPDATE_CHANNEL), "beta") ||
+      developerBuild ||
+      releaseCandidateOnBeta) {
     Preferences::SetBoolInAnyProcess(
       kTelemetryPref, true, PrefValueKind::Default);
   } else {
     Preferences::SetBoolInAnyProcess(
       kTelemetryPref, false, PrefValueKind::Default);
   }
   Preferences::LockInAnyProcess(kTelemetryPref);
 #endif // MOZ_WIDGET_ANDROID

--- a/toolkit/components/telemetry/TelemetryController.jsm
+++ b/toolkit/components/telemetry/TelemetryController.jsm
@@ -633,18 +633,22 @@ var Impl = {
       // on Release/ESR.
       let prereleaseChannels = ["nightly", "aurora", "beta"];
       if (!AppConstants.MOZILLA_OFFICIAL) {
         // Turn extended telemetry for local developer builds.
         prereleaseChannels.push("default");
       }
       const isPrereleaseChannel =
         prereleaseChannels.includes(AppConstants.MOZ_UPDATE_CHANNEL);
+      const isReleaseCandidateOnBeta =
+        AppConstants.MOZ_UPDATE_CHANNEL === "release" &&
+        Services.prefs.getCharPref("app.update.channel", null) === "beta";
       Telemetry.canRecordBase = true;
       Telemetry.canRecordExtended = isPrereleaseChannel ||
+        isReleaseCandidateOnBeta ||
         Services.prefs.getBoolPref(TelemetryUtils.Preferences.OverridePreRelease, false);
     } else {
       // We're not on unified Telemetry, stick to the old behaviour for
       // supporting Fennec.
       Telemetry.canRecordBase = Telemetry.canRecordExtended = Utils.isTelemetryEnabled;
     }
 
     this._log.config("enableTelemetryRecording - canRecordBase:" + Telemetry.canRecordBase +