diff --git a/harness/assert.js b/harness/assert.js
index 772ce49999..34eed55eef 100644
--- a/harness/assert.js
+++ b/harness/assert.js
@@ -66,6 +66,7 @@ assert.notSameValue = function (actual, unexpected, message) {
 };
 
 assert.throws = function (expectedErrorConstructor, func, message) {
+  var expectedName, actualName;
   if (typeof func !== "function") {
     throw new Test262Error('assert.throws requires two arguments: the error constructor ' +
       'and a function to run');
@@ -84,7 +85,13 @@ assert.throws = function (expectedErrorConstructor, func, message) {
       message += 'Thrown value was not an object!';
       throw new Test262Error(message);
     } else if (thrown.constructor !== expectedErrorConstructor) {
-      message += 'Expected a ' + expectedErrorConstructor.name + ' but got a ' + thrown.constructor.name;
+      expectedName = expectedErrorConstructor.name;
+      actualName = thrown.constructor.name;
+      if (expectedName === actualName) {
+        message += 'Expected a ' + expectedName + ' but got a different error constructor with the same name';
+      } else {
+        message += 'Expected a ' + expectedName + ' but got a ' + actualName;
+      }
       throw new Test262Error(message);
     }
     return;
diff --git a/test/harness/assert-throws-custom-typeerror.js b/test/harness/assert-throws-custom-typeerror.js
new file mode 100644
index 0000000000..1d7b651f41
--- /dev/null
+++ b/test/harness/assert-throws-custom-typeerror.js
@@ -0,0 +1,58 @@
+// Copyright (C) 2021 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: >
+    Functions that throw instances of the specified constructor function
+    satisfy the assertion, without collision with error constructors of the
+    same name.
+---*/
+
+var intrinsicTypeError = TypeError; 
+var threw = false;
+
+(function() {
+  function TypeError() {}
+
+  assert.throws(TypeError, function() {
+    throw new TypeError();
+  }, 'Throws an instance of the matching custom TypeError');
+
+  try {
+    assert.throws(intrinsicTypeError, function() {
+      throw new TypeError();
+    });
+  } catch (err) {
+    threw = true;
+    if (err.constructor !== Test262Error) {
+      throw new Error(
+        'Expected a Test262Error but a "' + err.constructor.name + 
+        '" was thrown.'
+      );
+    }
+  }
+
+  if (threw === false) {
+    throw new Error('Expected a Test262Error, but no error was thrown.');
+  }
+
+  threw = false;
+
+  try {
+    assert.throws(TypeError, function() {
+      throw new intrinsicTypeError();
+    });
+  } catch (err) {
+    threw = true;
+    if (err.constructor !== Test262Error) {
+      throw new Error(
+        'Expected a Test262Error but a "' + err.constructor.name + 
+        '" was thrown.'
+      );
+    }
+  }
+
+  if (threw === false) {
+    throw new Error('Expected a Test262Error, but no error was thrown.');
+  }
+})();
diff --git a/test/harness/assert-throws-same-realm.js b/test/harness/assert-throws-same-realm.js
new file mode 100644
index 0000000000..17f0443112
--- /dev/null
+++ b/test/harness/assert-throws-same-realm.js
@@ -0,0 +1,30 @@
+// Copyright (C) 2021 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: >
+    Functions that throw instances of the realm specified constructor function
+    satisfy the assertion, without cross realms collisions.
+---*/
+
+var intrinsicTypeError = TypeError; 
+var threw = false;
+var realmGlobal = $262.createRealm().global;
+
+try {
+  assert.throws(TypeError, function() {
+    throw new realmGlobal.TypeError();
+  });
+} catch (err) {
+  threw = true;
+  if (err.constructor !== Test262Error) {
+    throw new Error(
+      'Expected a Test262Error but a "' + err.constructor.name + 
+      '" was thrown.'
+    );
+  }
+}
+
+if (threw === false) {
+  throw new Error('Expected a Test262Error, but no error was thrown.');
+}