diff --git a/packages/underscore-tests/.gitignore b/packages/underscore-tests/.gitignore
new file mode 100644
index 0000000000..677a6fc263
--- /dev/null
+++ b/packages/underscore-tests/.gitignore
@@ -0,0 +1 @@
+.build*
diff --git a/packages/underscore-tests/each_test.js b/packages/underscore-tests/each_test.js
new file mode 100644
index 0000000000..50b071ee8d
--- /dev/null
+++ b/packages/underscore-tests/each_test.js
@@ -0,0 +1,45 @@
+Tinytest.add("underscore - each", function (test) {
+  // arrays
+  _.each([42], function (val, index) {
+    test.equal(index, 0);
+    test.equal(val, 42);
+  });
+
+  // objects with 'length' field aren't treated as arrays
+  _.each({length: 42}, function (val, key) {
+    test.equal(key, 'length');
+    test.equal(val, 42);
+  });
+
+  // The special 'arguments' variable is treated as an
+  // array
+  (function () {
+    _.each(arguments, function (val, index) {
+      test.equal(index, 0);
+      test.equal(val, 42);
+    });
+  })(42);
+
+  // An object with a 'callee' field isn't treated as arguments
+  _.each({callee: 42}, function (val, key) {
+    test.equal(key, 'callee');
+    test.equal(val, 42);
+  });
+
+  // An object with a 'callee' field isn't treated as arguments
+  _.each({length: 4, callee: 42}, function (val, key) {
+    if (key === 'callee')
+      test.equal(val, 42);
+    else if (key === 'length')
+      test.equal(val, 4);
+    else
+      test.fail({message: 'unexpected key: ' + key});
+  });
+
+
+  // NOTE: An object with a numberic 'length' field *and* a function
+  // 'callee' field will be treated as an array in IE. This may or may
+  // not be fixable, but isn't a big deal since: (1) 'callee' is a
+  // pretty rare key, and (2) JSON objects can't have functions
+  // anyways, which is the main use-case for _.each.
+});
diff --git a/packages/underscore-tests/package.js b/packages/underscore-tests/package.js
new file mode 100644
index 0000000000..0eb7218126
--- /dev/null
+++ b/packages/underscore-tests/package.js
@@ -0,0 +1,10 @@
+Package.describe({
+  // These tests can't be directly in the underscore packages since
+  // Tinytest depends on underscore
+  summary: "Tests for the underscore package"
+});
+
+Package.on_test(function (api) {
+  api.use(['tinytest', 'underscore']);
+  api.add_files('each_test.js');
+});
diff --git a/packages/underscore/underscore.js b/packages/underscore/underscore.js
index 3ffa3c111f..f5ca16aa33 100644
--- a/packages/underscore/underscore.js
+++ b/packages/underscore/underscore.js
@@ -81,7 +81,7 @@
   // there isn't any inspectable "Arguments" type.
   if (!_isArguments(arguments)) {
     _isArguments = function (obj) {
-      return !!(obj && hasOwnProperty.call(obj, 'callee'));
+      return !!(obj && hasOwnProperty.call(obj, 'callee') && typeof obj.callee === 'function');
     };
   }