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diff --git a/js/src/tests/test262/built-ins/String/prototype/trimStart/this-value-object-valueof-meth-priority.js b/js/src/tests/test262/built-ins/String/prototype/trimStart/this-value-object-valueof-meth-priority.js
new file mode 100644
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+++ b/js/src/tests/test262/built-ins/String/prototype/trimStart/this-value-object-valueof-meth-priority.js
@@ -0,0 +1,95 @@
+// Copyright (C) 2017 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-string.prototype.trimStart
+description: >
+  Priority of valueOf when converting object to string for trimming
+info: |
+  Runtime Semantics: TrimString ( string, where )
+  1. Let str be ? RequireObjectCoercible(string).
+  2. Let S be ? ToString(str).
+   ...
+
+  ToString ( argument )
+  If argument is Object:
+    1. Let primValue be ? ToPrimitive(argument, hint String).
+   ...
+
+  ToPrimitive ( input [, PreferredType ])
+   ...
+    b. Else if PreferredType is hint String, let hint be "string".
+   ...
+    d. Let exoticToPrim be ? GetMethod(input, @@toPrimitive)
+    e. If exoticToPrim is not undefined, then
+      i. Let result be ? Call(exoticToPrim, input, « hint »).
+      ii. If Type(result) is not Object, return result.
+      iii. Throw a TypeError exception.
+    f. If hint is "default", set hint to "number".
+    g. Return ? OrdinaryToPrimitive(input, hint).
+   ...
+
+  OrdinaryToPrimitive( O, hint )
+   ...
+    3. If hint is "string", then
+      a. Let methodNames be « "toString", "valueOf" ».
+   ...
+    5. For each name in methodNames in List order, do
+      a. Let method be ? Get(O, name).
+      b. If IsCallable(method) is true, then
+        i. Let result be ? Call(method, O).
+        ii. If Type(result) is not Object, return result.
+   ...
+features: [string-trimming, String.prototype.trimStart, Symbol.toPrimitive]
+---*/
+
+var toPrimitiveAccessed = 0;
+var toStringAccessed = 0;
+var valueOfAccessed = 0;
+var thisVal = {
+  get [Symbol.toPrimitive]() {
+    toPrimitiveAccessed += 1;
+    return undefined;
+  },
+  get toString() {
+    toStringAccessed += 1;
+    return undefined;
+  },
+  get valueOf() {
+    valueOfAccessed += 1;
+    return function() {
+      return ' 42';
+    };
+  },
+};
+
+// Test that valueOf is called when Symbol.toPrimitive and toString are both
+// undefined.
+
+var result = String.prototype.trimStart.call(thisVal);
+
+assert.sameValue(
+  valueOfAccessed,
+  1,
+  'thisVal.toString expected to have been accessed.'
+);
+assert.sameValue(
+  result,
+  '42',
+  'thisVal.valueOf expected to have been called.'
+);
+
+// Test that thisVal[toPrimitive] and thisVal.toString has been accessed.
+
+assert.sameValue(
+  toPrimitiveAccessed,
+  1,
+  'thisVal[Symbol.toPrimitive should have been accessed.'
+);
+assert.sameValue(
+  toStringAccessed,
+  1,
+  'thisVal[Symbol.toString should have been accessed.'
+);
+
+reportCompare(0, 0);