diff --git a/toolkit/components/normandy/actions/AddonRollbackAction.jsm b/toolkit/components/normandy/actions/AddonRollbackAction.jsm
index e4031df643af..a48c161c5c92 100644
--- a/toolkit/components/normandy/actions/AddonRollbackAction.jsm
+++ b/toolkit/components/normandy/actions/AddonRollbackAction.jsm
@@ -51,7 +51,12 @@ class AddonRollbackAction extends BaseAction {
               "unenrollFailed",
               "addon_rollback",
               rolloutSlug,
-              { reason: "uninstall-failed", enrollmentId: rollout.enrollmentId }
+              {
+                reason: "uninstall-failed",
+                enrollmentId:
+                  rollout.enrollmentId ||
+                  TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
+              }
             );
             throw err;
           }
@@ -65,7 +70,8 @@ class AddonRollbackAction extends BaseAction {
 
         TelemetryEvents.sendEvent("unenroll", "addon_rollback", rolloutSlug, {
           reason: "rollback",
-          enrollmentId: rollout.enrollmentId,
+          enrollmentId:
+            rollout.enrollmentId || TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
         });
         TelemetryEnvironment.setExperimentInactive(rolloutSlug);
         break;
diff --git a/toolkit/components/normandy/actions/AddonRolloutAction.jsm b/toolkit/components/normandy/actions/AddonRolloutAction.jsm
index 7e0276a476c9..e9c1ebb63ea5 100644
--- a/toolkit/components/normandy/actions/AddonRolloutAction.jsm
+++ b/toolkit/components/normandy/actions/AddonRolloutAction.jsm
@@ -118,7 +118,9 @@ class AddonRolloutAction extends BaseAction {
       const conflictError = createError("conflict", {
         addonId: conflictingRollout.addonId,
         conflictingSlug: conflictingRollout.slug,
-        enrollmentId: conflictingRollout.enrollmentId,
+        enrollmentId:
+          conflictingRollout.enrollmentId ||
+          TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
       });
       this.reportError(conflictError, "enrollFailed");
       throw conflictError;
@@ -129,7 +131,10 @@ class AddonRolloutAction extends BaseAction {
 
       if (existingRollout && existingRollout.addonId !== install.addon.id) {
         installDeferred.reject(
-          createError("addon-id-changed", { enrollmentId })
+          createError("addon-id-changed", {
+            enrollmentId:
+              enrollmentId || TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
+          })
         );
         return false; // cancel the upgrade, the add-on ID has changed
       }
@@ -139,7 +144,10 @@ class AddonRolloutAction extends BaseAction {
         Services.vc.compare(existingAddon.version, install.addon.version) > 0
       ) {
         installDeferred.reject(
-          createError("upgrade-required", { enrollmentId })
+          createError("upgrade-required", {
+            enrollmentId:
+              enrollmentId || TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
+          })
         );
         return false; // cancel the installation, must be an upgrade
       }
@@ -168,7 +176,7 @@ class AddonRolloutAction extends BaseAction {
           recipeId: recipe.id,
           state: AddonRollouts.STATE_ACTIVE,
           slug,
-          enrollmentId,
+          enrollmentId: enrollmentId || TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
           ...details,
         });
       }
@@ -211,7 +219,7 @@ class AddonRolloutAction extends BaseAction {
     TelemetryEvents.sendEvent(eventName, "addon_rollout", slug, {
       addonId: installedId,
       addonVersion: installedVersion,
-      enrollmentId,
+      enrollmentId: enrollmentId || TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
     });
   }
 
diff --git a/toolkit/components/normandy/actions/BranchedAddonStudyAction.jsm b/toolkit/components/normandy/actions/BranchedAddonStudyAction.jsm
index 67ae3db215d4..414079e12a79 100644
--- a/toolkit/components/normandy/actions/BranchedAddonStudyAction.jsm
+++ b/toolkit/components/normandy/actions/BranchedAddonStudyAction.jsm
@@ -353,7 +353,7 @@ class BranchedAddonStudyAction extends BaseStudyAction {
         addonId: AddonStudies.NO_ADDON_MARKER,
         addonVersion: AddonStudies.NO_ADDON_MARKER,
         branch: branch.slug,
-        enrollmentId,
+        enrollmentId: enrollmentId || TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
       });
     } else {
       const extensionDetails = await NormandyApi.fetchExtensionDetails(
@@ -435,13 +435,13 @@ class BranchedAddonStudyAction extends BaseStudyAction {
         addonId: installedId,
         addonVersion: installedVersion,
         branch: branch.slug,
-        enrollmentId,
+        enrollmentId: enrollmentId || TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
       });
     }
 
     TelemetryEnvironment.setExperimentActive(slug, branch.slug, {
       type: "normandy-addonstudy",
-      enrollmentId,
+      enrollmentId: enrollmentId || TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
     });
   }
 
@@ -474,7 +474,8 @@ class BranchedAddonStudyAction extends BaseStudyAction {
       error = new AddonStudyUpdateError(slug, {
         branch: branch.slug,
         reason: "addon-id-mismatch",
-        enrollmentId: study.enrollmentId,
+        enrollmentId:
+          study.enrollmentId || TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
       });
     }
 
@@ -486,7 +487,8 @@ class BranchedAddonStudyAction extends BaseStudyAction {
       error = new AddonStudyUpdateError(slug, {
         branch: branch.slug,
         reason: "no-downgrade",
-        enrollmentId: study.enrollmentId,
+        enrollmentId:
+          study.enrollmentId || TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
       });
     } else if (versionCompare === 0) {
       return; // Unchanged, do nothing
@@ -507,7 +509,8 @@ class BranchedAddonStudyAction extends BaseStudyAction {
           new AddonStudyUpdateError(slug, {
             branch: branch.slug,
             reason: "addon-does-not-exist",
-            enrollmentId: study.enrollmentId,
+            enrollmentId:
+              study.enrollmentId || TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
           })
         );
         return false; // cancel the installation, must upgrade an existing add-on
@@ -516,7 +519,8 @@ class BranchedAddonStudyAction extends BaseStudyAction {
           new AddonStudyUpdateError(slug, {
             branch: branch.slug,
             reason: "metadata-mismatch",
-            enrollmentId: study.enrollmentId,
+            enrollmentId:
+              study.enrollmentId || TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
           })
         );
         return false; // cancel the installation, server metadata do not match downloaded add-on
@@ -556,7 +560,10 @@ class BranchedAddonStudyAction extends BaseStudyAction {
       onFailedInstall,
       errorClass: AddonStudyUpdateError,
       reportError: this.reportUpdateError,
-      errorExtra: { enrollmentId: study.enrollmentId },
+      errorExtra: {
+        enrollmentId:
+          study.enrollmentId || TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
+      },
     });
 
     // All done, report success to Telemetry
@@ -564,7 +571,8 @@ class BranchedAddonStudyAction extends BaseStudyAction {
       addonId: installedId,
       addonVersion: installedVersion,
       branch: branch.slug,
-      enrollmentId: study.enrollmentId,
+      enrollmentId:
+        study.enrollmentId || TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
     });
   }
 
diff --git a/toolkit/components/normandy/actions/PreferenceRollbackAction.jsm b/toolkit/components/normandy/actions/PreferenceRollbackAction.jsm
index 0df18e0078ee..f87f7b8321e1 100644
--- a/toolkit/components/normandy/actions/PreferenceRollbackAction.jsm
+++ b/toolkit/components/normandy/actions/PreferenceRollbackAction.jsm
@@ -61,7 +61,11 @@ class PreferenceRollbackAction extends BaseAction {
           "unenroll",
           "preference_rollback",
           rolloutSlug,
-          { reason: "rollback", enrollmentId: rollout.enrollmentId }
+          {
+            reason: "rollback",
+            enrollmentId:
+              rollout.enrollmentId || TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
+          }
         );
         TelemetryEnvironment.setExperimentInactive(rolloutSlug);
         break;
@@ -76,7 +80,11 @@ class PreferenceRollbackAction extends BaseAction {
           "unenrollFailed",
           "preference_rollback",
           rolloutSlug,
-          { reason: "graduated", enrollmentId: rollout.enrollmentId }
+          {
+            reason: "graduated",
+            enrollmentId:
+              rollout.enrollmentId || TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
+          }
         );
         throw new Error(
           `Cannot rollback already graduated rollout ${rolloutSlug}`
diff --git a/toolkit/components/normandy/actions/PreferenceRolloutAction.jsm b/toolkit/components/normandy/actions/PreferenceRolloutAction.jsm
index 4110dfcd3b50..b5b92890eb9d 100644
--- a/toolkit/components/normandy/actions/PreferenceRolloutAction.jsm
+++ b/toolkit/components/normandy/actions/PreferenceRolloutAction.jsm
@@ -81,7 +81,9 @@ class PreferenceRolloutAction extends BaseAction {
         await PreferenceRollouts.update(newRollout);
         TelemetryEvents.sendEvent("update", "preference_rollout", args.slug, {
           previousState: existingRollout.state,
-          enrollmentId: existingRollout.enrollmentId,
+          enrollmentId:
+            existingRollout.enrollmentId ||
+            TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
         });
 
         switch (existingRollout.state) {
@@ -143,10 +145,10 @@ class PreferenceRolloutAction extends BaseAction {
       this.log.debug(`Enrolled in preference rollout ${args.slug}`);
       TelemetryEnvironment.setExperimentActive(args.slug, newRollout.state, {
         type: "normandy-prefrollout",
-        enrollmentId,
+        enrollmentId: enrollmentId || TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
       });
       TelemetryEvents.sendEvent("enroll", "preference_rollout", args.slug, {
-        enrollmentId,
+        enrollmentId: enrollmentId || TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
       });
     }
   }
diff --git a/toolkit/components/normandy/lib/AddonStudies.jsm b/toolkit/components/normandy/lib/AddonStudies.jsm
index 334f7d5162e4..8b847a4bbeb4 100644
--- a/toolkit/components/normandy/lib/AddonStudies.jsm
+++ b/toolkit/components/normandy/lib/AddonStudies.jsm
@@ -352,7 +352,8 @@ var AddonStudies = {
       addonVersion: study.addonVersion || AddonStudies.NO_ADDON_MARKER,
       reason,
       branch: study.branch,
-      enrollmentId: study.enrollmentId,
+      enrollmentId:
+        study.enrollmentId || TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
     });
     TelemetryEnvironment.setExperimentInactive(study.slug);
 
diff --git a/toolkit/components/normandy/lib/PreferenceExperiments.jsm b/toolkit/components/normandy/lib/PreferenceExperiments.jsm
index 0e8b727adb67..27cacdc44424 100644
--- a/toolkit/components/normandy/lib/PreferenceExperiments.jsm
+++ b/toolkit/components/normandy/lib/PreferenceExperiments.jsm
@@ -275,7 +275,8 @@ var PreferenceExperiments = {
         experiment.branch,
         {
           type: EXPERIMENT_TYPE_PREFIX + experiment.experimentType,
-          enrollmentId: experiment.enrollmentId,
+          enrollmentId:
+            experiment.enrollmentId || TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
         }
       );
 
@@ -551,12 +552,12 @@ var PreferenceExperiments = {
 
     TelemetryEnvironment.setExperimentActive(slug, branch, {
       type: EXPERIMENT_TYPE_PREFIX + experimentType,
-      enrollmentId,
+      enrollmentId: enrollmentId || TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
     });
     TelemetryEvents.sendEvent("enroll", "preference_study", slug, {
       experimentType,
       branch,
-      enrollmentId,
+      enrollmentId: enrollmentId || TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
     });
     await this.saveStartupPrefs();
 
@@ -712,7 +713,11 @@ var PreferenceExperiments = {
         "unenrollFailed",
         "preference_study",
         experimentSlug,
-        { reason: "already-unenrolled", enrollmentId: experiment.enrollmentId }
+        {
+          reason: "already-unenrolled",
+          enrollmentId:
+            experiment.enrollmentId || TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
+        }
       );
       throw new Error(
         `Cannot stop preference experiment "${experimentSlug}" because it is already expired`
@@ -764,7 +769,8 @@ var PreferenceExperiments = {
       didResetValue: resetValue ? "true" : "false",
       branch: experiment.branch,
       reason,
-      enrollmentId: experiment.enrollmentId,
+      enrollmentId:
+        experiment.enrollmentId || TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
     });
     await this.saveStartupPrefs();
   },
diff --git a/toolkit/components/normandy/lib/PreferenceRollouts.jsm b/toolkit/components/normandy/lib/PreferenceRollouts.jsm
index c3da3834a130..1546ac535e4d 100644
--- a/toolkit/components/normandy/lib/PreferenceRollouts.jsm
+++ b/toolkit/components/normandy/lib/PreferenceRollouts.jsm
@@ -156,7 +156,8 @@ var PreferenceRollouts = {
           "preference_rollout",
           rollout.slug,
           {
-            enrollmentId: rollout.enrollmentId,
+            enrollmentId:
+              rollout.enrollmentId || TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
           }
         );
       }
@@ -172,7 +173,8 @@ var PreferenceRollouts = {
     for (const rollout of await this.getAllActive()) {
       TelemetryEnvironment.setExperimentActive(rollout.slug, rollout.state, {
         type: "normandy-prefrollout",
-        enrollmentId: rollout.enrollmentId,
+        enrollmentId:
+          rollout.enrollmentId || TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
       });
     }
   },
diff --git a/toolkit/components/normandy/lib/TelemetryEvents.jsm b/toolkit/components/normandy/lib/TelemetryEvents.jsm
index 801fc57d306a..5b13bdf0c3c6 100644
--- a/toolkit/components/normandy/lib/TelemetryEvents.jsm
+++ b/toolkit/components/normandy/lib/TelemetryEvents.jsm
@@ -10,11 +10,20 @@ var EXPORTED_SYMBOLS = ["TelemetryEvents"];
 const TELEMETRY_CATEGORY = "normandy";
 
 const TelemetryEvents = {
+  NO_ENROLLMENT_ID_MARKER: "__NO_ENROLLMENT_ID__",
+
   init() {
     Services.telemetry.setEventRecordingEnabled(TELEMETRY_CATEGORY, true);
   },
 
   sendEvent(method, object, value, extra) {
+    for (const val of Object.values(extra)) {
+      if (val == null) {
+        throw new Error(
+          "Extra parameters in telemetry events must not be null"
+        );
+      }
+    }
     Services.telemetry.recordEvent(
       TELEMETRY_CATEGORY,
       method,