diff --git a/can-define.js b/can-define.js
index fe3b5c3..0e1703c 100644
--- a/can-define.js
+++ b/can-define.js
@@ -46,12 +46,14 @@ if(process.env.NODE_ENV !== 'production') {
 		if (definition.get) {
 			Object.defineProperty(definition.get, "name", {
 				value: "get "+canReflect.getName(obj) + "."+prop,
-				writable: true
+				writable: true,
+				configurable: true
 			});
 		}
 		if (definition.set) {
 			Object.defineProperty(definition.set, "name", {
-				value:  "set "+canReflect.getName(obj) + "."+prop
+				value:  "set "+canReflect.getName(obj) + "."+prop,
+				configurable: true
 			});
 		}
 		return Object.defineProperty(obj, prop, definition);
@@ -271,16 +273,19 @@ define.property = function(typePrototype, prop, definition, dataInitializers, co
 		if (definition.get) {
 			Object.defineProperty(definition.get, "name", {
 				value: canReflect.getName(typePrototype) + "'s " + prop + " getter",
+				configurable: true
 			});
 		}
 		if (definition.set) {
 			Object.defineProperty(definition.set, "name", {
 				value: canReflect.getName(typePrototype) + "'s " + prop + " setter",
+				configurable: true
 			});
 		}
 		if(isValueResolver(definition)) {
 			Object.defineProperty(definition.value, "name", {
 				value: canReflect.getName(typePrototype) + "'s " + prop + " value",
+				configurable: true
 			});
 		}
 	}
diff --git a/list/list.js b/list/list.js
index b92c778..b63c8eb 100644
--- a/list/list.js
+++ b/list/list.js
@@ -341,6 +341,7 @@ var eventsProtoSymbols = ("getOwnPropertySymbols" in Object) ?
 
 eventsProtoSymbols.forEach(function(sym) {
   Object.defineProperty(DefineList.prototype, sym, {
+  	configurable: true,
     enumerable:false,
     value: define.eventsProto[sym],
     writable: true
@@ -705,9 +706,8 @@ var defineListProto = {
 		var ret;
 		if(this._computed && this._computed[key] && this._computed[key].compute) {
 			ret = {};
-			ret.valueDependencies = new Set([
-				this._computed[key].compute
-			]);
+			ret.valueDependencies = new Set();
+			ret.valueDependencies.add(this._computed[key].compute);
 		}
 		return ret;
 	},
diff --git a/map/map-test.js b/map/map-test.js
index 21c5f72..c0c39e9 100644
--- a/map/map-test.js
+++ b/map/map-test.js
@@ -1439,6 +1439,28 @@ QUnit.test("expandos use default type (#383)", function(){
 });
 
 QUnit.test("do not enumerate anything other than key properties (#369)", function(){
+	// Internet Explorer doesn't correctly skip properties that are non-enumerable
+	// on the current object, but enumerable on the prototype:
+	var ancestor = { prop: true };
+	var F = function() {};
+	F.prototype = ancestor;
+	var descendant = new F();
+	Object.defineProperty(descendant, "prop", {
+		writable: true,
+		configurable: true,
+		enumerable: false,
+		value: true
+	});
+
+	var test = {};
+	for (var k in descendant) {
+		test[k] = descendant[k];
+	}
+	if (test.prop) {
+		return QUnit.ok(test.prop, "Browser doesn't correctly skip shadowed enumerable properties");
+	}
+
+
 	var Type = DefineMap.extend({
 		aProp: "string",
 		aMethod: function(){}
@@ -1447,7 +1469,7 @@ QUnit.test("do not enumerate anything other than key properties (#369)", functio
 	var instance = new Type({aProp: "VALUE", anExpando: "VALUE"});
 
 	var props = {};
-	for(var prop in instance) {
+	for (var prop in instance) {
 		props[prop] = true;
 	}
 	QUnit.deepEqual(props,{
diff --git a/map/map.js b/map/map.js
index da43756..417ac0f 100644
--- a/map/map.js
+++ b/map/map.js
@@ -251,9 +251,8 @@ var defineMapProto = {
 		var ret;
 		if(this._computed && this._computed[key] && this._computed[key].compute) {
 			ret = {};
-			ret.valueDependencies = new Set([
-				this._computed[key].compute
-			]);
+			ret.valueDependencies = new Set();
+			ret.valueDependencies.add(this._computed[key].compute);
 		}
 		return ret;
 	}
@@ -290,6 +289,7 @@ var eventsProtoSymbols = ("getOwnPropertySymbols" in Object) ?
 
 eventsProtoSymbols.forEach(function(sym) {
   Object.defineProperty(DefineMap.prototype, sym, {
+  	configurable: true,
     enumerable:false,
     value: define.eventsProto[sym],
     writable: true
diff --git a/test/test-define-only.js b/test/test-define-only.js
index 42967d3..415ea19 100644
--- a/test/test-define-only.js
+++ b/test/test-define-only.js
@@ -1216,10 +1216,10 @@ testHelpers.dev.devOnlyTest("Setting a value with only a get() generates a warni
 	QUnit.equal(finishErrorCheck(), 1);
 });
 
-testHelpers.dev.devOnlyTest("warn on using a Constructor for small-t type definintions", function() {
-	QUnit.expect(2);
+testHelpers.dev.devOnlyTest("warn on using a Constructor for small-t type definitions", function() {
+	QUnit.expect(1);
 
-	var message = 'can-define: the definition for VM{}.currency uses a constructor for "type". Did you mean "Type"?';
+	var message = /can-define: the definition for [\w{}\.]+ uses a constructor for "type"\. Did you mean "Type"\?/;
 	var finishErrorCheck = testHelpers.dev.willWarn(message);
 
 	function Currency() {
@@ -1241,27 +1241,12 @@ testHelpers.dev.devOnlyTest("warn on using a Constructor for small-t type defini
 
 	QUnit.equal(finishErrorCheck(), 1);
 
-	message = 'can-define: the definition for VM2{}.currency uses a constructor for "type". Did you mean "Type"?';
-	finishErrorCheck = testHelpers.dev.willWarn(message);
-
-	function VM2() {}
-
-	define(VM2.prototype, {
-		currency: {
-			type: Currency, // should be `Type: Currency`
-			default: function() {
-				return new Currency({});
-			}
-		}
-	});
-
-	QUnit.equal(finishErrorCheck(), 1);
 });
 
 testHelpers.dev.devOnlyTest("warn with constructor for Value instead of Default (#340)", function() {
 	QUnit.expect(1);
 
-	var message = "can-define: Change the 'Value' definition for VM{}.currency to 'Default'.";
+	var message = /can-define: Change the 'Value' definition for [\w\.{}]+.currency to 'Default'./;
 	var finishErrorCheck = testHelpers.dev.willWarn(message);
 
 	function Currency() {