diff --git a/js/public/Utility.h b/js/public/Utility.h
index 84cf9f09d169..e55b8a57bbc1 100644
--- a/js/public/Utility.h
+++ b/js/public/Utility.h
@@ -83,6 +83,7 @@ enum ThreadType {
  * mozilla::HelperThreadPool's runnable handler to call runTask() on each type.
  */
 struct RunnableTask {
+  virtual ThreadType threadType() = 0;
   virtual void runTask() = 0;
 };
 
diff --git a/js/src/gc/GCParallelTask.h b/js/src/gc/GCParallelTask.h
index c2b4c6d37919..eab605c718a9 100644
--- a/js/src/gc/GCParallelTask.h
+++ b/js/src/gc/GCParallelTask.h
@@ -99,6 +99,10 @@ class GCParallelTask : public RunnableTask {
 
   void runTask() override { func_(this); }
 
+  ThreadType threadType() override {
+    return ThreadType::THREAD_TYPE_GCPARALLEL;
+  }
+
  private:
   void assertNotStarted() const {
     // Don't lock here because that adds extra synchronization in debug
diff --git a/js/src/jit/IonBuilder.h b/js/src/jit/IonBuilder.h
index fea234eb60d9..437a234707fb 100644
--- a/js/src/jit/IonBuilder.h
+++ b/js/src/jit/IonBuilder.h
@@ -69,6 +69,9 @@ class IonBuilder : public MIRGenerator,
 
   void runTask() override;
 
+  // for use when ion compiles are being run offthread.
+  ThreadType threadType() override { return THREAD_TYPE_ION; }
+
  private:
   AbortReasonOr<Ok> traverseBytecode();
   AbortReasonOr<Ok> processIterators();
diff --git a/js/src/vm/HelperThreads.h b/js/src/vm/HelperThreads.h
index 32ad50771770..ec72df7e9c42 100644
--- a/js/src/vm/HelperThreads.h
+++ b/js/src/vm/HelperThreads.h
@@ -752,6 +752,7 @@ struct ParseTask : public mozilla::LinkedListElement<ParseTask>,
   }
 
   void runTask() override;
+  ThreadType threadType() override { return ThreadType::THREAD_TYPE_PARSE; }
 };
 
 struct ScriptDecodeTask : public ParseTask {
@@ -842,6 +843,8 @@ class SourceCompressionTask : public RunnableTask {
   void runTask() override;
   void complete();
 
+  ThreadType threadType() override { return ThreadType::THREAD_TYPE_COMPRESS; }
+
  private:
   struct PerformTaskWork;
   friend struct PerformTaskWork;
@@ -875,6 +878,7 @@ struct PromiseHelperTask : OffThreadPromiseTask, public RunnableTask {
   // the caller must immediately return from the stream callback.
   void executeAndResolveAndDestroy(JSContext* cx);
   void runTask() override;
+  ThreadType threadType() override { return THREAD_TYPE_PROMISE_TASK; }
 };
 
 } /* namespace js */
diff --git a/js/src/wasm/WasmGenerator.h b/js/src/wasm/WasmGenerator.h
index 42db9aff7aea..e3d7e15b414b 100644
--- a/js/src/wasm/WasmGenerator.h
+++ b/js/src/wasm/WasmGenerator.h
@@ -127,6 +127,7 @@ struct CompileTask : public RunnableTask {
   size_t sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const;
 
   void runTask() override;
+  ThreadType threadType() override { return ThreadType::THREAD_TYPE_WASM; }
 };
 
 // A ModuleGenerator encapsulates the creation of a wasm module. During the
diff --git a/js/src/wasm/WasmModule.cpp b/js/src/wasm/WasmModule.cpp
index 354c480fe913..7d8f7291e406 100644
--- a/js/src/wasm/WasmModule.cpp
+++ b/js/src/wasm/WasmModule.cpp
@@ -65,6 +65,9 @@ class Module::Tier2GeneratorTaskImpl : public Tier2GeneratorTask {
   void runTask() override {
     CompileTier2(*compileArgs_, bytecode_->bytes, *module_, &cancelled_);
   }
+  ThreadType threadType() override {
+    return ThreadType::THREAD_TYPE_WASM_TIER2;
+  }
 };
 
 Module::~Module() {