diff --git a/dom/bindings/test/TestBindingHeader.h b/dom/bindings/test/TestBindingHeader.h
index 8d33a0cb752..7743c931f35 100644
--- a/dom/bindings/test/TestBindingHeader.h
+++ b/dom/bindings/test/TestBindingHeader.h
@@ -55,6 +55,16 @@ public:
   virtual nsISupports* GetParentObject();
 
   // And now our actual WebIDL API
+  // Constructors
+  static
+  already_AddRefed<TestInterface> Constructor(nsISupports*, ErrorResult&);
+  static
+  already_AddRefed<TestInterface> Constructor(nsISupports*, const nsAString&,
+                                              ErrorResult&);
+  static
+  already_AddRefed<TestInterface> Constructor(nsISupports*, uint32_t,
+                                              Nullable<bool>&, ErrorResult&);
+
   // Integer types
   int8_t GetReadonlyByte(ErrorResult&);
   int8_t GetWritableByte(ErrorResult&);
diff --git a/dom/bindings/test/TestCodeGen.webidl b/dom/bindings/test/TestCodeGen.webidl
index b2fb54d3c7f..ee4807e3631 100644
--- a/dom/bindings/test/TestCodeGen.webidl
+++ b/dom/bindings/test/TestCodeGen.webidl
@@ -16,6 +16,9 @@ enum TestEnum {
 
 callback TestCallback = void();
 
+[Constructor,
+ Constructor(DOMString str),
+ Constructor(unsigned long num, boolean? bool)]
 interface TestInterface {
   // Integer types
   // XXXbz add tests for infallible versions of all the integer stuff