diff --git a/js/xpconnect/src/XPCQuickStubs.cpp b/js/xpconnect/src/XPCQuickStubs.cpp
index 4efe1addac0..4d2254ab745 100644
--- a/js/xpconnect/src/XPCQuickStubs.cpp
+++ b/js/xpconnect/src/XPCQuickStubs.cpp
@@ -149,60 +149,6 @@ castNative(JSContext *cx,
     return NS_ERROR_XPC_BAD_OP_ON_WN_PROTO;
 }
 
-nsISupports*
-castNativeFromWrapper(JSContext *cx,
-                      JSObject *obj,
-                      uint32_t interfaceBit,
-                      uint32_t protoID,
-                      int32_t protoDepth,
-                      nsISupports **pRef,
-                      MutableHandleValue pVal,
-                      nsresult *rv)
-{
-    XPCWrappedNative *wrapper;
-    XPCWrappedNativeTearOff *tearoff;
-    JSObject *cur;
-
-    if (IS_WN_REFLECTOR(obj)) {
-        cur = obj;
-        wrapper = XPCWrappedNative::Get(obj);
-        tearoff = nullptr;
-    } else {
-        *rv = getWrapper(cx, obj, &wrapper, &cur, &tearoff);
-        if (NS_FAILED(*rv))
-            return nullptr;
-    }
-
-    nsISupports *native;
-    if (wrapper) {
-        native = wrapper->GetIdentityObject();
-        cur = wrapper->GetFlatJSObject();
-        if (!native || !HasBitInInterfacesBitmap(cur, interfaceBit)) {
-            native = nullptr;
-        }
-    } else if (cur && protoDepth >= 0) {
-        const mozilla::dom::DOMJSClass* domClass =
-            mozilla::dom::GetDOMClass(cur);
-        native = mozilla::dom::UnwrapDOMObject<nsISupports>(cur);
-        if (native &&
-            (uint32_t)domClass->mInterfaceChain[protoDepth] != protoID) {
-            native = nullptr;
-        }
-    } else {
-        native = nullptr;
-    }
-
-    if (native) {
-        *pRef = nullptr;
-        pVal.setObjectOrNull(cur);
-        *rv = NS_OK;
-    } else {
-        *rv = NS_ERROR_XPC_BAD_CONVERT_JS;
-    }
-
-    return native;
-}
-
 nsresult
 xpc_qsUnwrapArgImpl(JSContext *cx,
                     HandleValue v,
diff --git a/js/xpconnect/src/XPCQuickStubs.h b/js/xpconnect/src/XPCQuickStubs.h
index 0aad7f8a0b4..3ea26e97472 100644
--- a/js/xpconnect/src/XPCQuickStubs.h
+++ b/js/xpconnect/src/XPCQuickStubs.h
@@ -28,16 +28,6 @@ castNative(JSContext *cx,
            nsISupports **ppThisRef,
            JS::MutableHandleValue vp);
 
-nsISupports*
-castNativeFromWrapper(JSContext *cx,
-                      JSObject *obj,
-                      uint32_t interfaceBit,
-                      uint32_t protoID,
-                      int32_t protoDepth,
-                      nsISupports **pRef,
-                      JS::MutableHandleValue pVal,
-                      nsresult *rv);
-
 MOZ_ALWAYS_INLINE JSObject*
 xpc_qsUnwrapObj(jsval v, nsISupports **ppArgRef, nsresult *rv)
 {
@@ -60,21 +50,4 @@ nsresult
 xpc_qsUnwrapArgImpl(JSContext *cx, JS::HandleValue v, const nsIID &iid, void **ppArg,
                     nsISupports **ppArgRef, JS::MutableHandleValue vp);
 
-MOZ_ALWAYS_INLINE nsISupports*
-castNativeArgFromWrapper(JSContext *cx,
-                         jsval v,
-                         uint32_t bit,
-                         uint32_t protoID,
-                         int32_t protoDepth,
-                         nsISupports **pArgRef,
-                         JS::MutableHandleValue vp,
-                         nsresult *rv)
-{
-    JSObject *src = xpc_qsUnwrapObj(v, pArgRef, rv);
-    if (!src)
-        return nullptr;
-
-    return castNativeFromWrapper(cx, src, bit, protoID, protoDepth, pArgRef, vp, rv);
-}
-
 #endif /* xpcquickstubs_h___ */