--- a/toolkit/components/telemetry/TelemetryEnvironment.jsm
+++ b/toolkit/components/telemetry/TelemetryEnvironment.jsm
@@ -47,16 +47,21 @@ const MAX_EXPERIMENT_TYPE_LENGTH = 20;
 
 /**
  * This is a policy object used to override behavior for testing.
  */
 var Policy = {
   now: () => new Date(),
 };
 
+// This is used to buffer calls to setExperimentActive and friends, so that we
+// don't prematurely initialize our environment if it is called early during
+// startup.
+var gActiveExperimentStartupBuffer = new Map();
+
 var gGlobalEnvironment;
 function getGlobal() {
   if (!gGlobalEnvironment) {
     gGlobalEnvironment = new EnvironmentCache();
   }
   return gGlobalEnvironment;
 }
 
@@ -87,41 +92,57 @@ this.TelemetryEnvironment = {
    * This triggers a new subsession, subject to throttling.
    *
    * @param {String} id The id of the active experiment.
    * @param {String} branch The experiment branch.
    * @param {Object} [options] Optional object with options.
    * @param {String} [options.type=false] The specific experiment type.
    */
   setExperimentActive(id, branch, options = {}) {
-    return getGlobal().setExperimentActive(id, branch, options);
+    if (gGlobalEnvironment) {
+      gGlobalEnvironment.setExperimentActive(id, branch, options);
+    } else {
+      gActiveExperimentStartupBuffer.set(id, {branch, options});
+    }
   },
 
   /**
    * Remove an experiment annotation from the environment.
    * If the annotation exists, a new subsession will triggered.
    *
    * @param {String} id The id of the active experiment.
    */
   setExperimentInactive(id) {
-    return getGlobal().setExperimentInactive(id);
+    if (gGlobalEnvironment) {
+      gGlobalEnvironment.setExperimentInactive(id);
+    } else {
+      gActiveExperimentStartupBuffer.delete(id);
+    }
   },
 
   /**
    * Returns an object containing the data for the active experiments.
    *
    * The returned object is of the format:
    *
    * {
    *   "<experiment id>": { branch: "<branch>" },
    *   // …
    * }
    */
   getActiveExperiments() {
-    return getGlobal().getActiveExperiments();
+    if (gGlobalEnvironment) {
+      return gGlobalEnvironment.getActiveExperiments();
+    }
+
+    const result = {};
+    for (const [id, {branch}] of gActiveExperimentStartupBuffer.entries()) {
+      result[id] = branch;
+    }
+    return result;
   },
 
   shutdown() {
     return getGlobal().shutdown();
   },
 
   // Policy to use when saving preferences. Exported for using them in tests.
   RECORD_PREF_STATE: 1, // Don't record the preference value
@@ -146,16 +167,17 @@ this.TelemetryEnvironment = {
   },
 
   /**
    * Intended for use in tests only.
    */
   testCleanRestart() {
     getGlobal().shutdown();
     gGlobalEnvironment = null;
+    gActiveExperimentStartupBuffer = new Map();
     return getGlobal();
   },
 };
 
 const RECORD_PREF_STATE = TelemetryEnvironment.RECORD_PREF_STATE;
 const RECORD_PREF_VALUE = TelemetryEnvironment.RECORD_PREF_VALUE;
 const RECORD_DEFAULTPREF_VALUE = TelemetryEnvironment.RECORD_DEFAULTPREF_VALUE;
 const DEFAULT_ENVIRONMENT_PREFS = new Map([
@@ -841,16 +863,21 @@ function EnvironmentCache() {
   p = [ this._addonBuilder.init() ];
 
   this._currentEnvironment.profile = {};
   p.push(this._updateProfile());
   if (AppConstants.MOZ_BUILD_APP == "browser") {
     p.push(this._updateAttribution());
   }
 
+  for (const [id, {branch, options}] of gActiveExperimentStartupBuffer.entries()) {
+    this.setExperimentActive(id, branch, options);
+  }
+  gActiveExperimentStartupBuffer = null;
+
   let setup = () => {
     this._initTask = null;
     this._startWatchingPrefs();
     this._addonBuilder.watchForChanges();
     this._updateGraphicsFeatures();
     return this.currentEnvironment;
   };