--- a/dom/base/nsDOMJSUtils.h
+++ b/dom/base/nsDOMJSUtils.h
@@ -29,20 +29,17 @@ GetScriptContextFromJSContext(JSContext 
   // released, but that's ok here.
   return scx;
 }
 
 JSObject* GetDefaultScopeFromJSContext(JSContext *cx);
 
 // A factory function for turning a JS::Value argv into an nsIArray
 // but also supports an effecient way of extracting the original argv.
-// Bug 312003 describes why this must be "void *", but argv will be cast to
-// JS::Value* and the args are found at:
-//    ((JS::Value*)aArgv)[0], ..., ((JS::Value*)aArgv)[aArgc - 1]
 // The resulting object will take a copy of the array, and ensure each
 // element is rooted.
 // Optionally, aArgv may be nullptr, in which case the array is allocated and
 // rooted, but all items remain nullptr.  This presumably means the caller
 // will then QI us for nsIJSArgArray, and set our array elements.
-nsresult NS_CreateJSArgv(JSContext *aContext, uint32_t aArgc, void *aArgv,
-                         nsIJSArgArray **aArray);
+nsresult NS_CreateJSArgv(JSContext *aContext, uint32_t aArgc,
+                         const JS::Value* aArgv, nsIJSArgArray **aArray);
 
 #endif // nsDOMJSUtils_h__

--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@@ -7839,17 +7839,17 @@ nsGlobalWindow::OpenDialog(JSContext* aC
                            ErrorResult& aError)
 {
   FORWARD_TO_OUTER_OR_THROW(OpenDialog,
                             (aCx, aUrl, aName, aOptions, aExtraArgument, aError),
                             aError, nullptr);
 
   nsCOMPtr<nsIJSArgArray> argvArray;
   aError = NS_CreateJSArgv(aCx, aExtraArgument.Length(),
-                           const_cast<JS::Value*>(aExtraArgument.Elements()),
+                           aExtraArgument.Elements(),
                            getter_AddRefs(argvArray));
   if (aError.Failed()) {
     return nullptr;
   }
 
   nsCOMPtr<nsIDOMWindow> dialog;
   aError = OpenInternal(aUrl, aName, aOptions,
                         true,             // aDialog

--- a/dom/base/nsJSEnvironment.cpp
+++ b/dom/base/nsJSEnvironment.cpp
@@ -2863,17 +2863,17 @@ mozilla::dom::ShutdownJSEnvironment()
 // A fast-array class for JS.  This class supports both nsIJSScriptArray and
 // nsIArray.  If it is JS itself providing and consuming this class, all work
 // can be done via nsIJSScriptArray, and avoid the conversion of elements
 // to/from nsISupports.
 // When consumed by non-JS (eg, another script language), conversion is done
 // on-the-fly.
 class nsJSArgArray final : public nsIJSArgArray {
 public:
-  nsJSArgArray(JSContext *aContext, uint32_t argc, JS::Value *argv,
+  nsJSArgArray(JSContext *aContext, uint32_t argc, const JS::Value* argv,
                nsresult *prv);
 
   // nsISupports
   NS_DECL_CYCLE_COLLECTING_ISUPPORTS
   NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS_AMBIGUOUS(nsJSArgArray,
                                                          nsIJSArgArray)
 
   // nsIArray
@@ -2886,21 +2886,21 @@ public:
 
 protected:
   ~nsJSArgArray();
   JSContext *mContext;
   JS::Heap<JS::Value> *mArgv;
   uint32_t mArgc;
 };
 
-nsJSArgArray::nsJSArgArray(JSContext *aContext, uint32_t argc, JS::Value *argv,
-                           nsresult *prv) :
-    mContext(aContext),
-    mArgv(nullptr),
-    mArgc(argc)
+nsJSArgArray::nsJSArgArray(JSContext *aContext, uint32_t argc,
+                           const JS::Value* argv, nsresult *prv)
+  : mContext(aContext)
+  , mArgv(nullptr)
+  , mArgc(argc)
 {
   // copy the array - we don't know its lifetime, and ours is tied to xpcom
   // refcounting.
   if (argc) {
     mArgv = new (fallible) JS::Heap<JS::Value>[argc];
     if (!mArgv) {
       *prv = NS_ERROR_OUT_OF_MEMORY;
       return;
@@ -3005,20 +3005,19 @@ NS_IMETHODIMP nsJSArgArray::IndexOf(uint
 
 /* nsISimpleEnumerator enumerate (); */
 NS_IMETHODIMP nsJSArgArray::Enumerate(nsISimpleEnumerator **_retval)
 {
   return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 // The factory function
-nsresult NS_CreateJSArgv(JSContext *aContext, uint32_t argc, void *argv,
-                         nsIJSArgArray **aArray)
+nsresult NS_CreateJSArgv(JSContext *aContext, uint32_t argc,
+                         const JS::Value* argv, nsIJSArgArray **aArray)
 {
   nsresult rv;
-  nsCOMPtr<nsIJSArgArray> ret = new nsJSArgArray(aContext, argc,
-                                                static_cast<JS::Value *>(argv), &rv);
+  nsCOMPtr<nsIJSArgArray> ret = new nsJSArgArray(aContext, argc, argv, &rv);
   if (NS_FAILED(rv)) {
     return rv;
   }
   ret.forget(aArray);
   return NS_OK;
 }