diff --git a/es5-shim.js b/es5-shim.js
index ffc9a131..b851f71f 100644
--- a/es5-shim.js
+++ b/es5-shim.js
@@ -135,11 +135,22 @@
         $Object.defineProperty(F, 'prototype', { value: sentinel, writable: false });
         if ((new F()).toString !== toStringSentinel) {
             var $dP = $Object.defineProperty;
+            var $gOPD = $Object.getOwnPropertyDescriptor;
             defineProperties($Object, {
                 defineProperty: function defineProperty(o, k, d) {
                     var key = $String(k);
-                    if (key === 'prototype' && 'writable' in d && 'value' in d) {
-                        o[key] = d.value; // eslint-disable-line no-param-reassign
+                    if (typeof o === 'function' && key === 'prototype') {
+                        var desc = $gOPD(o, key);
+                        if (desc.writable && !d.writable && 'value' in d) {
+                            try {
+                                o[key] = d.value; // eslint-disable-line no-param-reassign
+                            } catch (e) { /**/ }
+                        }
+                        return $dP(o, key, {
+                            configurable: 'configurable' in d ? d.configurable : desc.configurable,
+                            enumerable: 'enumerable' in d ? d.enumerable : desc.enumerable,
+                            writable: d.writable
+                        });
                     }
                     return $dP(o, key, d);
                 }
diff --git a/tests/spec/s-object.js b/tests/spec/s-object.js
index 2b7e8c8f..6af28ebc 100644
--- a/tests/spec/s-object.js
+++ b/tests/spec/s-object.js
@@ -12,6 +12,7 @@ var supportsDescriptors = Object.defineProperty && (function () {
         return false;
     }
 }());
+var ifSupportsDescriptorsIt = supportsDescriptors ? it : xit;
 var ifWindowIt = typeof window === 'undefined' ? xit : it;
 var extensionsPreventible = typeof Object.preventExtensions === 'function' && (function () {
     var obj = {};
@@ -248,7 +249,7 @@ describe('Object', function () {
             }).not.toThrow();
         });
 
-        (supportsDescriptors ? it : xit)('allows setting a nonwritable prototype', function () {
+        ifSupportsDescriptorsIt('allows setting a nonwritable prototype', function () {
             var F = function () {};
             expect(F.prototype).toEqual(Object.getOwnPropertyDescriptor(F, 'prototype').value);
             expect((new F()).toString).toEqual(Object.prototype.toString);
@@ -264,6 +265,24 @@ describe('Object', function () {
             expect(F.prototype).toEqual(Object.getOwnPropertyDescriptor(F, 'prototype').value);
             expect((new F()).toString).toEqual(toStringSentinel);
         });
+
+        ifSupportsDescriptorsIt('properly makes a prototype non-writable', function () {
+            var O = { prototype: 1 };
+            expect(O.prototype).toEqual(Object.getOwnPropertyDescriptor(O, 'prototype').value);
+            expect(O.prototype).toEqual(1);
+
+            expect(function () {
+                Object.defineProperty(O, 'prototype', { writable: false, configurable: true });
+            }).not.toThrow();
+
+            var sentinel = {};
+            expect(function () {
+                Object.defineProperty(O, 'prototype', { value: sentinel });
+            }).not.toThrow();
+
+            expect(O.prototype).toEqual(Object.getOwnPropertyDescriptor(O, 'prototype').value);
+            expect(O.prototype).toEqual(sentinel);
+        });
     });
 
     describe('.getOwnPropertyDescriptor()', function () {