--- a/js/src/builtin/SIMD.cpp
+++ b/js/src/builtin/SIMD.cpp
@@ -297,53 +297,46 @@ CreateSimdClass(JSContext *cx, Handle<Gl
 
     return typeDescr;
 }
 
 bool
 SimdTypeDescr::call(JSContext *cx, unsigned argc, Value *vp)
 {
     CallArgs args = CallArgsFromVp(argc, vp);
-    const unsigned LANES = 4;
 
     Rooted<SimdTypeDescr*> descr(cx, &args.callee().as<SimdTypeDescr>());
     if (args.length() == 1) {
         // SIMD type used as a coercion
         if (!CheckVectorObject(args[0], descr->type())) {
             JS_ReportErrorNumber(cx, js_GetErrorMessage, nullptr, JSMSG_SIMD_NOT_A_VECTOR);
             return false;
         }
 
         args.rval().setObject(args[0].toObject());
         return true;
     }
 
-    if (args.length() < LANES) {
-        JS_ReportErrorNumber(cx, js_GetErrorMessage, nullptr, JSMSG_MORE_ARGS_NEEDED,
-                             args.callee().getClass()->name, "3", "s");
-        return false;
-    }
-
     Rooted<TypedObject*> result(cx, TypedObject::createZeroed(cx, descr, 0));
     if (!result)
         return false;
 
     switch (descr->type()) {
       case SimdTypeDescr::TYPE_INT32: {
         int32_t *mem = reinterpret_cast<int32_t*>(result->typedMem());
         for (unsigned i = 0; i < 4; i++) {
-            if (!ToInt32(cx, args[i], &mem[i]))
+            if (!ToInt32(cx, args.get(i), &mem[i]))
                 return false;
         }
         break;
       }
       case SimdTypeDescr::TYPE_FLOAT32: {
         float *mem = reinterpret_cast<float*>(result->typedMem());
         for (unsigned i = 0; i < 4; i++) {
-            if (!RoundFloat32(cx, args[i], &mem[i]))
+            if (!RoundFloat32(cx, args.get(i), &mem[i]))
                 return false;
         }
         break;
       }
     }
     args.rval().setObject(*result);
     return true;
 }

deleted file mode 100644
--- a/js/src/tests/ecma_7/SIMD/coercions.js
+++ /dev/null
@@ -1,66 +0,0 @@
-// |reftest| skip-if(!this.hasOwnProperty("SIMD"))
-var BUGNUMBER = 1061229;
-var float32x4 = SIMD.float32x4;
-var int32x4 = SIMD.int32x4;
-var {StructType, int32} = TypedObject;
-var summary = 'constructors used as coercions';
-
-/*
- * Any copyright is dedicated to the Public Domain.
- * http://creativecommons.org/licenses/publicdomain/
- */
-
-function assertCaught(f) {
-    var caught = false;
-    var args = Array.slice(arguments, 1);
-    try {
-        f.apply(null, args);
-    } catch (e) {
-        caught = true;
-        print(e)
-    }
-    assertEq(caught, true);
-}
-
-function test() {
-    var x = int32x4(1, 2, 3, 4);
-    var y = int32x4(x);
-
-    assertEq(x, y);
-
-    assertEq(y.x, x.x);
-    assertEq(y.x, 1);
-    assertEq(y.y, x.y);
-    assertEq(y.y, 2);
-    assertEq(y.z, x.z);
-    assertEq(y.z, 3);
-    assertEq(y.w, x.w);
-    assertEq(y.w, 4);
-
-    assertCaught(int32x4, 3);
-    assertCaught(int32x4, float32x4(1, 2, 3, 4));
-    assertCaught(int32x4, 'pony x 4');
-
-    var x = float32x4(NaN, 13.37, -Infinity, 4);
-    var y = float32x4(x);
-
-    assertEq(x, y);
-
-    assertEq(y.x, x.x);
-    assertEq(y.x, Math.fround(NaN));
-    assertEq(y.y, x.y);
-    assertEq(y.y, Math.fround(13.37));
-    assertEq(y.z, x.z);
-    assertEq(y.z, Math.fround(-Infinity));
-    assertEq(y.w, x.w);
-    assertEq(y.w, Math.fround(4));
-
-    assertCaught(float32x4, 3);
-    assertCaught(float32x4, int32x4(1, 2, 3, 4));
-    assertCaught(float32x4, 'pony x 4');
-
-    if (typeof reportCompare === "function")
-        reportCompare(true, true);
-}
-
-test();

new file mode 100644
--- /dev/null
+++ b/js/src/tests/ecma_7/SIMD/constructors.js
@@ -0,0 +1,66 @@
+// |reftest| skip-if(!this.hasOwnProperty("SIMD"))
+
+var float32x4 = SIMD.float32x4;
+var int32x4 = SIMD.int32x4;
+
+function test() {
+
+    // Constructors.
+    assertEqX4(int32x4(1, 2, 3, 4),         [1,2,3,4]);
+    assertEqX4(int32x4(1, 2, 3),            [1,2,3,0]);
+    assertEqX4(int32x4(1, 2),               [1,2,0,0]);
+    // The 1-argument form is reserved for coercions.
+    assertEqX4(int32x4(),                   [0,0,0,0]);
+    assertEqX4(int32x4(1, 2, 3, 4, 5),      [1,2,3,4]);
+    assertEqX4(int32x4(1, 2, 3, 4, 5, 6),   [1,2,3,4]);
+
+    assertEqX4(float32x4(1, 2, 3, 4),       [1,2,3,4]);
+    assertEqX4(float32x4(1, 2, 3),          [1,2,3,NaN]);
+    assertEqX4(float32x4(1, 2),             [1,2,NaN,NaN]);
+    // The 1-argument form is reserved for coercions.
+    assertEqX4(float32x4(),                 [NaN,NaN,NaN,NaN]);
+    assertEqX4(float32x4(1, 2, 3, 4, 5),    [1,2,3,4]);
+    assertEqX4(float32x4(1, 2, 3, 4, 5, 6), [1,2,3,4]);
+
+    // Constructors used as coercion.
+    var x = int32x4(1, 2, 3, 4);
+    var y = int32x4(x);
+
+    assertEq(x, y);
+
+    assertEq(y.x, x.x);
+    assertEq(y.x, 1);
+    assertEq(y.y, x.y);
+    assertEq(y.y, 2);
+    assertEq(y.z, x.z);
+    assertEq(y.z, 3);
+    assertEq(y.w, x.w);
+    assertEq(y.w, 4);
+
+    assertThrowsInstanceOf(() => int32x4(3), TypeError);
+    assertThrowsInstanceOf(() => int32x4(float32x4(1,2,3,4)), TypeError);
+    assertThrowsInstanceOf(() => int32x4('pony x 4'), TypeError);
+
+    var x = float32x4(NaN, 13.37, -Infinity, 4);
+    var y = float32x4(x);
+
+    assertEq(x, y);
+
+    assertEq(y.x, x.x);
+    assertEq(y.x, Math.fround(NaN));
+    assertEq(y.y, x.y);
+    assertEq(y.y, Math.fround(13.37));
+    assertEq(y.z, x.z);
+    assertEq(y.z, Math.fround(-Infinity));
+    assertEq(y.w, x.w);
+    assertEq(y.w, Math.fround(4));
+
+    assertThrowsInstanceOf(() => float32x4(3), TypeError);
+    assertThrowsInstanceOf(() => float32x4(int32x4(1,2,3,4)), TypeError);
+    assertThrowsInstanceOf(() => float32x4('pony x 4'), TypeError);
+
+    if (typeof reportCompare === "function")
+        reportCompare(true, true);
+}
+
+test();