--- a/js/src/shell/js.cpp
+++ b/js/src/shell/js.cpp
@@ -3538,33 +3538,33 @@ WorkerMain(void* arg)
     JSContext* cx = input->parentRuntime
          ? JS_NewContext(8L * 1024L * 1024L, 2L * 1024L * 1024L, input->parentRuntime)
          : JS_NewCooperativeContext(input->siblingContext);
     if (!cx)
         return;
 
     SetCooperativeYieldCallback(cx, CooperativeYieldCallback);
 
-    UniquePtr<ShellContext> sc = MakeUnique<ShellContext>(cx);
+    ShellContext* sc = js_new<ShellContext>(cx);
     if (!sc)
         return;
 
     auto guard = mozilla::MakeScopeExit([&] {
-        if (cx)
-            JS_DestroyContext(cx);
+        JS_DestroyContext(cx);
+        js_delete(sc);
         if (input->siblingContext) {
             cooperationState->numThreads--;
             CooperativeYield();
         }
         js_delete(input);
     });
 
     if (input->parentRuntime)
         sc->isWorker = true;
-    JS_SetContextPrivate(cx, sc.get());
+    JS_SetContextPrivate(cx, sc);
     SetWorkerContextOptions(cx);
     JS::SetBuildIdOp(cx, ShellBuildId);
 
     Maybe<EnvironmentPreparer> environmentPreparer;
     if (input->parentRuntime) {
         JS_SetFutexCanWait(cx);
         JS::SetWarningReporter(cx, WarningReporter);
         js::SetPreserveWrapperCallback(cx, DummyPreserveWrapperCallback);
@@ -3576,17 +3576,17 @@ WorkerMain(void* arg)
             return;
 
         environmentPreparer.emplace(cx);
     } else {
         JS_AddInterruptCallback(cx, ShellInterruptCallback);
 
         // The Gecko Profiler requires that all cooperating contexts have
         // profiling stacks installed.
-        MOZ_ALWAYS_TRUE(EnsureGeckoProfilingStackInstalled(cx, sc.get()));
+        MOZ_ALWAYS_TRUE(EnsureGeckoProfilingStackInstalled(cx, sc));
     }
 
     do {
         JSAutoRequest ar(cx);
 
         JS::CompartmentOptions compartmentOptions;
         SetStandardCompartmentOptions(compartmentOptions);
         if (input->siblingContext)