diff --git a/dom/workers/ServiceWorkerManager.cpp b/dom/workers/ServiceWorkerManager.cpp
index 6686e212ce..0bea0223f8 100644
--- a/dom/workers/ServiceWorkerManager.cpp
+++ b/dom/workers/ServiceWorkerManager.cpp
@@ -3154,10 +3154,12 @@ already_AddRefed<ServiceWorkerRegistrationInfo>
 ServiceWorkerManager::CreateNewRegistration(const nsCString& aScope,
                                             nsIPrincipal* aPrincipal)
 {
+  nsresult rv;
+
 #ifdef DEBUG
   AssertIsOnMainThread();
   nsCOMPtr<nsIURI> scopeURI;
-  nsresult rv = NS_NewURI(getter_AddRefs(scopeURI), aScope, nullptr, nullptr);
+  rv = NS_NewURI(getter_AddRefs(scopeURI), aScope, nullptr, nullptr);
   MOZ_ASSERT(NS_SUCCEEDED(rv));
 
   RefPtr<ServiceWorkerRegistrationInfo> tmp =
@@ -3165,8 +3167,35 @@ ServiceWorkerManager::CreateNewRegistration(const nsCString& aScope,
   MOZ_ASSERT(!tmp);
 #endif
 
+  // The environment that registers the document may have some CSP applied
+  // to its principal.  This should not be inherited by the registration
+  // itself or the worker it creates.  To avoid confusion in callsites
+  // downstream we strip the CSP from the principal now.
+  //
+  // Unfortunately there is no API to clone a principal without its CSP.  To
+  // achieve the same thing we serialize to the IPC PrincipalInfo type and
+  // back to an nsIPrincipal.
+  PrincipalInfo principalInfo;
+  rv = PrincipalToPrincipalInfo(aPrincipal, &principalInfo);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return nullptr;
+  }
+
+  nsCOMPtr<nsIPrincipal> cleanPrincipal =
+    PrincipalInfoToPrincipal(principalInfo, &rv);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return nullptr;
+  }
+
+  // Verify that we do not have any CSP set on our principal "clone".
+#if defined(DEBUG) || !defined(RELEASE_OR_BETA)
+  nsCOMPtr<nsIContentSecurityPolicy> csp;
+  MOZ_ALWAYS_SUCCEEDS(cleanPrincipal->GetCsp(getter_AddRefs(csp)));
+  MOZ_DIAGNOSTIC_ASSERT(!csp);
+#endif
+
   RefPtr<ServiceWorkerRegistrationInfo> registration =
-    new ServiceWorkerRegistrationInfo(aScope, aPrincipal);
+    new ServiceWorkerRegistrationInfo(aScope, cleanPrincipal);
   // From now on ownership of registration is with
   // mServiceWorkerRegistrationInfos.
   AddScopeAndRegistration(aScope, registration);
diff --git a/dom/workers/ServiceWorkerRegisterJob.cpp b/dom/workers/ServiceWorkerRegisterJob.cpp
index 30f0772ea6..6a97259d5f 100644
--- a/dom/workers/ServiceWorkerRegisterJob.cpp
+++ b/dom/workers/ServiceWorkerRegisterJob.cpp
@@ -52,6 +52,11 @@ ServiceWorkerRegisterJob::AsyncExecute()
     }
   } else {
     registration = swm->CreateNewRegistration(mScope, mPrincipal);
+
+    if (!registration) {
+      FailUpdateJob(NS_ERROR_DOM_ABORT_ERR);
+      return;
+    }
   }
 
   SetRegistration(registration);