diff --git a/js/src/builtin/MapObject.cpp b/js/src/builtin/MapObject.cpp
index 973823d26ed3..60504bcb0393 100644
--- a/js/src/builtin/MapObject.cpp
+++ b/js/src/builtin/MapObject.cpp
@@ -1236,14 +1236,13 @@ MapObject::finalize(FreeOp* fop, JSObject* obj)
 bool
 MapObject::construct(JSContext* cx, unsigned argc, Value* vp)
 {
-    Rooted<MapObject*> obj(cx, MapObject::create(cx));
-    if (!obj)
-        return false;
-
     CallArgs args = CallArgsFromVp(argc, vp);
 
-    // FIXME: bug 1083752
-    if (!WarnIfNotConstructing(cx, args, "Map"))
+    if (!ThrowIfNotConstructing(cx, args, "Map"))
+        return false;
+
+    Rooted<MapObject*> obj(cx, MapObject::create(cx));
+    if (!obj)
         return false;
 
     if (!args.get(0).isNullOrUndefined()) {
@@ -1902,14 +1901,13 @@ SetObject::finalize(FreeOp* fop, JSObject* obj)
 bool
 SetObject::construct(JSContext* cx, unsigned argc, Value* vp)
 {
-    Rooted<SetObject*> obj(cx, SetObject::create(cx));
-    if (!obj)
-        return false;
-
     CallArgs args = CallArgsFromVp(argc, vp);
 
-    // FIXME: bug 1083752
-    if (!WarnIfNotConstructing(cx, args, "Set"))
+    if (!ThrowIfNotConstructing(cx, args, "Set"))
+        return false;
+
+    Rooted<SetObject*> obj(cx, SetObject::create(cx));
+    if (!obj)
         return false;
 
     if (!args.get(0).isNullOrUndefined()) {
diff --git a/js/src/jit-test/tests/collections/Map-constructor-1.js b/js/src/jit-test/tests/collections/Map-constructor-1.js
index 528f43cc2340..b1a55967dc8a 100644
--- a/js/src/jit-test/tests/collections/Map-constructor-1.js
+++ b/js/src/jit-test/tests/collections/Map-constructor-1.js
@@ -9,8 +9,6 @@ assertEq(m.size, 0);
 m = new Map(null);
 assertEq(m.size, 0);
 
-// FIXME: bug 1083752
-assertWarning(() => Map(), "None");
-// assertThrowsInstanceOf(() => Map(), TypeError);
-// assertThrowsInstanceOf(() => Map(undefined), TypeError);
-// assertThrowsInstanceOf(() => Map(null), TypeError);
+assertThrowsInstanceOf(() => Map(), TypeError);
+assertThrowsInstanceOf(() => Map(undefined), TypeError);
+assertThrowsInstanceOf(() => Map(null), TypeError);
diff --git a/js/src/jit-test/tests/collections/Set-constructor-1.js b/js/src/jit-test/tests/collections/Set-constructor-1.js
index 47913f869160..eab36af90930 100644
--- a/js/src/jit-test/tests/collections/Set-constructor-1.js
+++ b/js/src/jit-test/tests/collections/Set-constructor-1.js
@@ -9,8 +9,6 @@ assertEq(s.size, 0);
 s = new Set(null);
 assertEq(s.size, 0);
 
-// FIXME: bug 1083752
-assertWarning(() => Set(), "None");
-// assertThrowsInstanceOf(() => Set(), TypeError);
-// assertThrowsInstanceOf(() => Set(undefined), TypeError);
-// assertThrowsInstanceOf(() => Set(null), TypeError);
+assertThrowsInstanceOf(() => Set(), TypeError);
+assertThrowsInstanceOf(() => Set(undefined), TypeError);
+assertThrowsInstanceOf(() => Set(null), TypeError);
diff --git a/js/src/jit-test/tests/collections/WeakMap-constructor-1.js b/js/src/jit-test/tests/collections/WeakMap-constructor-1.js
index bfeaa2511a3f..ab73feb51cee 100644
--- a/js/src/jit-test/tests/collections/WeakMap-constructor-1.js
+++ b/js/src/jit-test/tests/collections/WeakMap-constructor-1.js
@@ -6,8 +6,6 @@ new WeakMap();
 new WeakMap(undefined);
 new WeakMap(null);
 
-// FIXME: bug 1083752
-assertWarning(() => WeakMap(), "None");
-// assertThrowsInstanceOf(() => WeakMap(), TypeError);
-// assertThrowsInstanceOf(() => WeakMap(undefined), TypeError);
-// assertThrowsInstanceOf(() => WeakMap(null), TypeError);
+assertThrowsInstanceOf(() => WeakMap(), TypeError);
+assertThrowsInstanceOf(() => WeakMap(undefined), TypeError);
+assertThrowsInstanceOf(() => WeakMap(null), TypeError);
diff --git a/js/src/jsweakmap.cpp b/js/src/jsweakmap.cpp
index 3d835ae6982c..ddd8c4e5a22c 100644
--- a/js/src/jsweakmap.cpp
+++ b/js/src/jsweakmap.cpp
@@ -512,13 +512,13 @@ static bool
 WeakMap_construct(JSContext* cx, unsigned argc, Value* vp)
 {
     CallArgs args = CallArgsFromVp(argc, vp);
-    RootedObject obj(cx, NewBuiltinClassInstance(cx, &WeakMapObject::class_));
-    if (!obj)
-        return false;
 
     // ES6 draft rev 31 (15 Jan 2015) 23.3.1.1 step 1.
-    // FIXME: bug 1083752
-    if (!WarnIfNotConstructing(cx, args, "WeakMap"))
+    if (!ThrowIfNotConstructing(cx, args, "WeakMap"))
+        return false;
+
+    RootedObject obj(cx, NewBuiltinClassInstance(cx, &WeakMapObject::class_));
+    if (!obj)
         return false;
 
     // Steps 5-6, 11.