diff --git a/test/built-ins/String/prototype/trimStart/this-value-object-toprimitive-returns-object-err.js b/test/built-ins/String/prototype/trimStart/this-value-object-toprimitive-returns-object-err.js
new file mode 100644
index 00000000000..becaf421b38
--- /dev/null
+++ b/test/built-ins/String/prototype/trimStart/this-value-object-toprimitive-returns-object-err.js
@@ -0,0 +1,38 @@
+// 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: >
+    Abrupt completion when Symbol.toPrimitive returns an object
+info: |
+  Runtime Semantics: TrimString ( string, where )
+  1. Let str be ? RequireObjectCoercible(string).
+  2. Let S be ? ToString(str).
+   ...
+
+  ToString ( argument )
+  If arguement is Object:
+    1. Let primValue be ? ToPrimitive(argument, hint String).
+   ...
+
+  ToPrimitive ( input [, PreferredType ])
+   ...
+    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.
+   ...
+features: [string-trimming, Symbol.toPrimitive]
+---*/
+
+var thisVal = {
+  [Symbol.toPrimitive]: function() {
+    return {};
+  },
+};
+
+assert.throws(TypeError, function() {
+  String.prototype.trimStart.call(thisVal);
+});
diff --git a/test/built-ins/String/prototype/trimStart/this-value-object-tostring-returns-object-err.js b/test/built-ins/String/prototype/trimStart/this-value-object-tostring-returns-object-err.js
new file mode 100644
index 00000000000..c55b81e1749
--- /dev/null
+++ b/test/built-ins/String/prototype/trimStart/this-value-object-tostring-returns-object-err.js
@@ -0,0 +1,56 @@
+// 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: >
+  Abrupt completion when toString called and returns an object
+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.
+    6. Throw a TypeError exception.
+features: [string-trimming, Symbol.toPrimitive]
+---*/
+
+
+var thisVal = {
+  [Symbol.toPrimitive]: undefined,
+  toString: function() {
+    return {};
+  },
+};
+
+assert.throws(TypeError, function() {
+  String.prototype.trimStart.call(thisVal);
+});
diff --git a/test/built-ins/String/prototype/trimStart/this-value-object-valueof-returns-object-err.js b/test/built-ins/String/prototype/trimStart/this-value-object-valueof-returns-object-err.js
new file mode 100644
index 00000000000..b89e636ee82
--- /dev/null
+++ b/test/built-ins/String/prototype/trimStart/this-value-object-valueof-returns-object-err.js
@@ -0,0 +1,57 @@
+// 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: >
+  Abrupt completion when valueOf called and returns an object
+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.
+    6. Throw a TypeError exception.
+features: [string-trimming, Symbol.toPrimitive]
+---*/
+
+
+var thisVal = {
+  [Symbol.toPrimitive]: undefined,
+  toString: undefined,
+  valueOf: function() {
+    return {};
+  },
+};
+
+assert.throws(TypeError, function() {
+  String.prototype.trimStart.call(thisVal);
+});