diff --git a/xpcom/threads/nsThreadUtils.h b/xpcom/threads/nsThreadUtils.h
index 7d2cb37090ca..63e5a5298761 100644
--- a/xpcom/threads/nsThreadUtils.h
+++ b/xpcom/threads/nsThreadUtils.h
@@ -382,7 +382,7 @@ public:
   NS_DECL_NSIRUNNABLE
   NS_DECL_NSINAMED
 
-  Runnable() {}
+  Runnable() = delete;
 
 #ifdef RELEASE_OR_BETA
   explicit Runnable(const char* aName) {}
@@ -412,7 +412,7 @@ public:
   // nsICancelableRunnable
   virtual nsresult Cancel() override;
 
-  CancelableRunnable() {}
+  CancelableRunnable() = delete;
   explicit CancelableRunnable(const char* aName) : Runnable(aName) {}
 
 protected: