diff --git a/lib/6to5/traverse/scope.js b/lib/6to5/traverse/scope.js
index f6cc050998..eaa82a51b2 100644
--- a/lib/6to5/traverse/scope.js
+++ b/lib/6to5/traverse/scope.js
@@ -63,38 +63,29 @@ Scope.prototype.generateUidBasedOnNode = function (parent, file) {
     node = parent.left;
   } else if (t.isVariableDeclarator(parent)) {
     node = parent.id;
-  }
-
-  var id = "ref";
-
-  if (t.isProperty(node)) {
+  } else if (t.isProperty(node)) {
     node = node.key;
   }
 
-  if (t.isIdentifier(node)) {
-    id = node.name;
-  } else if (t.isLiteral(node)) {
-    id = node.value;
-  } else if (t.isMemberExpression(node)) {
-    var parts = [];
+  var parts = [];
 
-    var add = function (node) {
-      if (t.isMemberExpression(node)) {
-        add(node.object);
-        add(node.property);
-      } else if (t.isIdentifier(node)) {
-        parts.push(node.name);
-      } else if (t.isLiteral(node)) {
-        parts.push(node.value);
-      }
-    };
+  var add = function (node) {
+    if (t.isMemberExpression(node)) {
+      add(node.object);
+      add(node.property);
+    } else if (t.isIdentifier(node)) {
+      parts.push(node.name);
+    } else if (t.isLiteral(node)) {
+      parts.push(node.value);
+    } else if (t.isCallExpression(node)) {
+      add(node.callee);
+    }
+  };
 
-    add(node);
+  add(node);
 
-    id = parts.join("$");
-  }
-
-  id = id.replace(/^_/, "");
+  var id = parts.join("$");
+  id = id.replace(/^_/, "") || "ref";
 
   return file.generateUidIdentifier(id, this);
 };
@@ -108,10 +99,6 @@ Scope.prototype.generateUidBasedOnNode = function (parent, file) {
  */
 
 Scope.prototype.generateTempBasedOnNode = function (node, file) {
-  if (!t.isIdentifier(node) && !t.isMemberExpression(node)) {
-    throw new TypeError("Invalid node type " + JSON.stringify(node.type) + " passed to Scope.prototype.generateTempBasedOnNode");
-  }
-
   if (t.isIdentifier(node) && this.has(node.name, true)) {
     return null;
   }
diff --git a/test/fixtures/transformation/es6-classes/accessing-super-class/expected.js b/test/fixtures/transformation/es6-classes/accessing-super-class/expected.js
index 1eec391c5e..14f12f07e2 100644
--- a/test/fixtures/transformation/es6-classes/accessing-super-class/expected.js
+++ b/test/fixtures/transformation/es6-classes/accessing-super-class/expected.js
@@ -22,8 +22,8 @@ var Test = (function () {
     _Foo.prototype.test.call(this);
     foob(_Foo);
 
-    _Foo.call.apply(null, [this].concat(_slice.call(arguments)));
-    _Foo.call.apply(null, [this, "test"].concat(_slice.call(arguments)));
+    _Foo.call.apply(_Foo, [this].concat(_slice.call(arguments)));
+    _Foo.call.apply(_Foo, [this, "test"].concat(_slice.call(arguments)));
 
     (_Foo$prototype$test = _Foo.prototype.test).call.apply(_Foo$prototype$test, [this].concat(_slice.call(arguments)));
     (_Foo$prototype$test2 = _Foo.prototype.test).call.apply(_Foo$prototype$test2, [this, "test"].concat(_slice.call(arguments)));
diff --git a/test/fixtures/transformation/optional-proto-to-assign/assignment-expression/expected.js b/test/fixtures/transformation/optional-proto-to-assign/assignment-expression/expected.js
index 6a66b4e972..9de37223a2 100644
--- a/test/fixtures/transformation/optional-proto-to-assign/assignment-expression/expected.js
+++ b/test/fixtures/transformation/optional-proto-to-assign/assignment-expression/expected.js
@@ -1,6 +1,6 @@
 "use strict";
 
-var _foo, _foo$bar, _foo2;
+var _foo, _foo$bar, _foo$bar2;
 var _defaults = function (obj, defaults) {
   for (var key in defaults) {
     if (obj[key] === undefined) {
@@ -15,4 +15,4 @@ console.log((_foo = foo, _defaults(_foo, bar), _foo));
 
 console.log((_foo$bar = foo[bar], _defaults(_foo$bar, bar), _foo$bar));
 
-console.log((_foo2 = foo[bar()], _defaults(_foo2, bar), _foo2));
+console.log((_foo$bar2 = foo[bar()], _defaults(_foo$bar2, bar), _foo$bar2));
diff --git a/test/fixtures/transformation/playground/memoization-assignment-operator/expected.js b/test/fixtures/transformation/playground/memoization-assignment-operator/expected.js
index 4d9647c912..fbb64ac4f8 100644
--- a/test/fixtures/transformation/playground/memoization-assignment-operator/expected.js
+++ b/test/fixtures/transformation/playground/memoization-assignment-operator/expected.js
@@ -1,6 +1,6 @@
 "use strict";
 
-var _obj2, _obj4, _ref2, _obj6, _ref4;
+var _obj2, _obj4, _x2, _obj$y2, _x4;
 var _hasOwn = Object.prototype.hasOwnProperty;
 var obj = {};
 
@@ -11,17 +11,17 @@ if (!_hasOwn.call(_obj, "x")) _obj.x = 2;
 console.log((_obj2 = obj, !_hasOwn.call(_obj2, "x") && (_obj2.x = 2), _obj2.x));
 
 var _obj3 = obj;
-var _ref = x();
+var _x = x();
 
-if (!_hasOwn.call(_obj3, _ref)) _obj3[_ref] = 2;
+if (!_hasOwn.call(_obj3, _x)) _obj3[_x] = 2;
 
 
-console.log((_obj4 = obj, _ref2 = x(), !_hasOwn.call(_obj4, _ref2) && (_obj4[_ref2] = 2), _obj4[_ref2]));
+console.log((_obj4 = obj, _x2 = x(), !_hasOwn.call(_obj4, _x2) && (_obj4[_x2] = 2), _obj4[_x2]));
 
-var _obj5 = obj[y()];
-var _ref3 = x();
+var _obj$y = obj[y()];
+var _x3 = x();
 
-if (!_hasOwn.call(_obj5, _ref3)) _obj5[_ref3] = 2;
+if (!_hasOwn.call(_obj$y, _x3)) _obj$y[_x3] = 2;
 
 
-console.log((_obj6 = obj[y()], _ref4 = x(), !_hasOwn.call(_obj6, _ref4) && (_obj6[_ref4] = 2), _obj6[_ref4]));
+console.log((_obj$y2 = obj[y()], _x4 = x(), !_hasOwn.call(_obj$y2, _x4) && (_obj$y2[_x4] = 2), _obj$y2[_x4]));
diff --git a/test/fixtures/transformation/playground/method-binding/expected.js b/test/fixtures/transformation/playground/method-binding/expected.js
index f103f4683f..156bcfffd5 100644
--- a/test/fixtures/transformation/playground/method-binding/expected.js
+++ b/test/fixtures/transformation/playground/method-binding/expected.js
@@ -1,11 +1,11 @@
 "use strict";
 
-var _obj, _obj2, _obj$foo, _obj$foo2, _obj3, _args, _args2, _args3;
+var _obj, _obj2, _obj$foo, _obj$foo2, _obj$foo3, _args, _args2, _args3;
 var fn = (_obj = obj, _obj.method.bind(_obj));
 var fn = (_obj2 = obj, _obj2.method.bind(_obj2, "foob"));
 var fn = (_obj$foo = obj[foo], _obj$foo.method.bind(_obj$foo));
 var fn = (_obj$foo2 = obj.foo, _obj$foo2.method.bind(_obj$foo2));
-var fn = (_obj3 = obj[foo()], _obj3.method.bind(_obj3));
+var fn = (_obj$foo3 = obj[foo()], _obj$foo3.method.bind(_obj$foo3));
 
 ["foo", "bar"].map((_args = [], function (_val) {
   return _val.toUpperCase();