diff --git a/bower.json b/bower.json
index f564e732..49a018f1 100644
--- a/bower.json
+++ b/bower.json
@@ -1,6 +1,6 @@
 {
   "name": "aurelia-binding",
-  "version": "1.0.6",
+  "version": "1.0.7",
   "description": "A modern databinding library for JavaScript and HTML.",
   "license": "MIT",
   "keywords": [
diff --git a/dist/amd/aurelia-binding.js b/dist/amd/aurelia-binding.js
index 7bb8220b..ded7a1d8 100644
--- a/dist/amd/aurelia-binding.js
+++ b/dist/amd/aurelia-binding.js
@@ -3692,7 +3692,7 @@ define(['exports', 'aurelia-logging', 'aurelia-pal', 'aurelia-task-queue', 'aure
     StyleObserver.prototype._setProperty = function _setProperty(style, value) {
       var priority = '';
 
-      if (value.indexOf('!important') !== -1) {
+      if (value.indexOf && value.indexOf('!important') !== -1) {
         priority = 'important';
         value = value.replace('!important', '');
       }
@@ -5312,12 +5312,17 @@ define(['exports', 'aurelia-logging', 'aurelia-pal', 'aurelia-task-queue', 'aure
       }
 
       var innerPropertyName = '_' + key;
+      var innerPropertyDescriptor = {
+        configurable: true,
+        enumerable: false,
+        writable: true
+      };
 
       var callbackName = config && config.changeHandler || key + 'Changed';
 
       if (descriptor) {
         if (typeof descriptor.initializer === 'function') {
-          target[innerPropertyName] = descriptor.initializer();
+          innerPropertyDescriptor.value = descriptor.initializer();
         }
       } else {
         descriptor = {};
@@ -5327,15 +5332,21 @@ define(['exports', 'aurelia-logging', 'aurelia-pal', 'aurelia-task-queue', 'aure
         descriptor.enumerable = true;
       }
 
+      delete descriptor.value;
       delete descriptor.writable;
       delete descriptor.initializer;
 
+      Reflect.defineProperty(target, innerPropertyName, innerPropertyDescriptor);
+
       descriptor.get = function () {
         return this[innerPropertyName];
       };
       descriptor.set = function (newValue) {
         var oldValue = this[innerPropertyName];
+
         this[innerPropertyName] = newValue;
+        Reflect.defineProperty(this, innerPropertyName, { enumerable: false });
+
         if (this[callbackName]) {
           this[callbackName](newValue, oldValue, key);
         }
diff --git a/dist/aurelia-binding.js b/dist/aurelia-binding.js
index 994a717d..ffbc19b8 100644
--- a/dist/aurelia-binding.js
+++ b/dist/aurelia-binding.js
@@ -3511,7 +3511,7 @@ export class StyleObserver {
   _setProperty(style, value) {
     let priority = '';
 
-    if (value.indexOf('!important') !== -1) {
+    if (value.indexOf && value.indexOf('!important') !== -1) {
       priority = 'important';
       value = value.replace('!important', '');
     }
@@ -5040,6 +5040,11 @@ export function observable(targetOrConfig: any, key: string, descriptor?: Proper
 
     // use a convention to compute the inner property name
     let innerPropertyName = `_${key}`;
+    const innerPropertyDescriptor: PropertyDescriptor = {
+      configurable: true,
+      enumerable: false,
+      writable: true
+    };
 
     // determine callback name based on config or convention.
     const callbackName = (config && config.changeHandler) || `${key}Changed`;
@@ -5049,7 +5054,7 @@ export function observable(targetOrConfig: any, key: string, descriptor?: Proper
 
       // set the initial value of the property if it is defined.
       if (typeof descriptor.initializer === 'function') {
-        target[innerPropertyName] = descriptor.initializer();
+        innerPropertyDescriptor.value = descriptor.initializer();
       }
     } else {
       // there is no descriptor if the target was a field in TS (although Babel provides one),
@@ -5063,14 +5068,22 @@ export function observable(targetOrConfig: any, key: string, descriptor?: Proper
 
     // we're adding a getter and setter which means the property descriptor
     // cannot have a "value" or "writable" attribute
+    delete descriptor.value;
     delete descriptor.writable;
     delete descriptor.initializer;
 
+    // Add the inner property on the prototype.
+    Reflect.defineProperty(target, innerPropertyName, innerPropertyDescriptor);
+
     // add the getter and setter to the property descriptor.
     descriptor.get = function() { return this[innerPropertyName]; };
     descriptor.set = function(newValue) {
       let oldValue = this[innerPropertyName];
+
+      // Add the inner property on the instance and make it nonenumerable.
       this[innerPropertyName] = newValue;
+      Reflect.defineProperty(this, innerPropertyName, { enumerable: false });
+
       if (this[callbackName]) {
         this[callbackName](newValue, oldValue, key);
       }
diff --git a/dist/commonjs/aurelia-binding.js b/dist/commonjs/aurelia-binding.js
index c000d7e3..0cd1eb51 100644
--- a/dist/commonjs/aurelia-binding.js
+++ b/dist/commonjs/aurelia-binding.js
@@ -3645,7 +3645,7 @@ var StyleObserver = exports.StyleObserver = function () {
   StyleObserver.prototype._setProperty = function _setProperty(style, value) {
     var priority = '';
 
-    if (value.indexOf('!important') !== -1) {
+    if (value.indexOf && value.indexOf('!important') !== -1) {
       priority = 'important';
       value = value.replace('!important', '');
     }
@@ -5265,12 +5265,17 @@ function observable(targetOrConfig, key, descriptor) {
     }
 
     var innerPropertyName = '_' + key;
+    var innerPropertyDescriptor = {
+      configurable: true,
+      enumerable: false,
+      writable: true
+    };
 
     var callbackName = config && config.changeHandler || key + 'Changed';
 
     if (descriptor) {
       if (typeof descriptor.initializer === 'function') {
-        target[innerPropertyName] = descriptor.initializer();
+        innerPropertyDescriptor.value = descriptor.initializer();
       }
     } else {
       descriptor = {};
@@ -5280,15 +5285,21 @@ function observable(targetOrConfig, key, descriptor) {
       descriptor.enumerable = true;
     }
 
+    delete descriptor.value;
     delete descriptor.writable;
     delete descriptor.initializer;
 
+    Reflect.defineProperty(target, innerPropertyName, innerPropertyDescriptor);
+
     descriptor.get = function () {
       return this[innerPropertyName];
     };
     descriptor.set = function (newValue) {
       var oldValue = this[innerPropertyName];
+
       this[innerPropertyName] = newValue;
+      Reflect.defineProperty(this, innerPropertyName, { enumerable: false });
+
       if (this[callbackName]) {
         this[callbackName](newValue, oldValue, key);
       }
diff --git a/dist/es2015/aurelia-binding.js b/dist/es2015/aurelia-binding.js
index 8a827da3..e1fe273f 100644
--- a/dist/es2015/aurelia-binding.js
+++ b/dist/es2015/aurelia-binding.js
@@ -3346,7 +3346,7 @@ export let StyleObserver = class StyleObserver {
   _setProperty(style, value) {
     let priority = '';
 
-    if (value.indexOf('!important') !== -1) {
+    if (value.indexOf && value.indexOf('!important') !== -1) {
       priority = 'important';
       value = value.replace('!important', '');
     }
@@ -4806,12 +4806,17 @@ export function observable(targetOrConfig, key, descriptor) {
     }
 
     let innerPropertyName = `_${ key }`;
+    const innerPropertyDescriptor = {
+      configurable: true,
+      enumerable: false,
+      writable: true
+    };
 
     const callbackName = config && config.changeHandler || `${ key }Changed`;
 
     if (descriptor) {
       if (typeof descriptor.initializer === 'function') {
-        target[innerPropertyName] = descriptor.initializer();
+        innerPropertyDescriptor.value = descriptor.initializer();
       }
     } else {
       descriptor = {};
@@ -4821,15 +4826,21 @@ export function observable(targetOrConfig, key, descriptor) {
       descriptor.enumerable = true;
     }
 
+    delete descriptor.value;
     delete descriptor.writable;
     delete descriptor.initializer;
 
+    Reflect.defineProperty(target, innerPropertyName, innerPropertyDescriptor);
+
     descriptor.get = function () {
       return this[innerPropertyName];
     };
     descriptor.set = function (newValue) {
       let oldValue = this[innerPropertyName];
+
       this[innerPropertyName] = newValue;
+      Reflect.defineProperty(this, innerPropertyName, { enumerable: false });
+
       if (this[callbackName]) {
         this[callbackName](newValue, oldValue, key);
       }
diff --git a/dist/native-modules/aurelia-binding.js b/dist/native-modules/aurelia-binding.js
index f435e639..9643689a 100644
--- a/dist/native-modules/aurelia-binding.js
+++ b/dist/native-modules/aurelia-binding.js
@@ -3610,7 +3610,7 @@ export var StyleObserver = function () {
   StyleObserver.prototype._setProperty = function _setProperty(style, value) {
     var priority = '';
 
-    if (value.indexOf('!important') !== -1) {
+    if (value.indexOf && value.indexOf('!important') !== -1) {
       priority = 'important';
       value = value.replace('!important', '');
     }
@@ -5227,12 +5227,17 @@ export function observable(targetOrConfig, key, descriptor) {
     }
 
     var innerPropertyName = '_' + key;
+    var innerPropertyDescriptor = {
+      configurable: true,
+      enumerable: false,
+      writable: true
+    };
 
     var callbackName = config && config.changeHandler || key + 'Changed';
 
     if (descriptor) {
       if (typeof descriptor.initializer === 'function') {
-        target[innerPropertyName] = descriptor.initializer();
+        innerPropertyDescriptor.value = descriptor.initializer();
       }
     } else {
       descriptor = {};
@@ -5242,15 +5247,21 @@ export function observable(targetOrConfig, key, descriptor) {
       descriptor.enumerable = true;
     }
 
+    delete descriptor.value;
     delete descriptor.writable;
     delete descriptor.initializer;
 
+    Reflect.defineProperty(target, innerPropertyName, innerPropertyDescriptor);
+
     descriptor.get = function () {
       return this[innerPropertyName];
     };
     descriptor.set = function (newValue) {
       var oldValue = this[innerPropertyName];
+
       this[innerPropertyName] = newValue;
+      Reflect.defineProperty(this, innerPropertyName, { enumerable: false });
+
       if (this[callbackName]) {
         this[callbackName](newValue, oldValue, key);
       }
diff --git a/dist/system/aurelia-binding.js b/dist/system/aurelia-binding.js
index 20060ebc..0026f415 100644
--- a/dist/system/aurelia-binding.js
+++ b/dist/system/aurelia-binding.js
@@ -815,12 +815,17 @@ System.register(['aurelia-logging', 'aurelia-pal', 'aurelia-task-queue', 'aureli
       }
 
       var innerPropertyName = '_' + key;
+      var innerPropertyDescriptor = {
+        configurable: true,
+        enumerable: false,
+        writable: true
+      };
 
       var callbackName = config && config.changeHandler || key + 'Changed';
 
       if (descriptor) {
         if (typeof descriptor.initializer === 'function') {
-          target[innerPropertyName] = descriptor.initializer();
+          innerPropertyDescriptor.value = descriptor.initializer();
         }
       } else {
         descriptor = {};
@@ -830,15 +835,21 @@ System.register(['aurelia-logging', 'aurelia-pal', 'aurelia-task-queue', 'aureli
         descriptor.enumerable = true;
       }
 
+      delete descriptor.value;
       delete descriptor.writable;
       delete descriptor.initializer;
 
+      Reflect.defineProperty(target, innerPropertyName, innerPropertyDescriptor);
+
       descriptor.get = function () {
         return this[innerPropertyName];
       };
       descriptor.set = function (newValue) {
         var oldValue = this[innerPropertyName];
+
         this[innerPropertyName] = newValue;
+        Reflect.defineProperty(this, innerPropertyName, { enumerable: false });
+
         if (this[callbackName]) {
           this[callbackName](newValue, oldValue, key);
         }
@@ -3900,7 +3911,7 @@ System.register(['aurelia-logging', 'aurelia-pal', 'aurelia-task-queue', 'aureli
         StyleObserver.prototype._setProperty = function _setProperty(style, value) {
           var priority = '';
 
-          if (value.indexOf('!important') !== -1) {
+          if (value.indexOf && value.indexOf('!important') !== -1) {
             priority = 'important';
             value = value.replace('!important', '');
           }
diff --git a/doc/CHANGELOG.md b/doc/CHANGELOG.md
index 3eb9b93e..87a4c2fe 100644
--- a/doc/CHANGELOG.md
+++ b/doc/CHANGELOG.md
@@ -1,3 +1,15 @@
+<a name="1.0.7"></a>
+## [1.0.7](https://github.com/aurelia/binding/compare/1.0.6...v1.0.7) (2016-10-05)
+
+
+### Bug Fixes
+
+* **observable:** backing property should not be enumerable ([521270b](https://github.com/aurelia/binding/commit/521270b))
+* **observable:** handle descriptor with set ([fa3dafb](https://github.com/aurelia/binding/commit/fa3dafb)), closes [#511](https://github.com/aurelia/binding/issues/511)
+* **StyleObserver:** handle numbers ([ca4933d](https://github.com/aurelia/binding/commit/ca4933d)), closes [#518](https://github.com/aurelia/binding/issues/518)
+
+
+
 <a name="1.0.6"></a>
 ## [1.0.6](https://github.com/aurelia/binding/compare/1.0.5...v1.0.6) (2016-09-29)
 
diff --git a/doc/example-dist/binding-checkboxes/objects-matcher/app.html b/doc/example-dist/binding-checkboxes/objects-matcher/app.html
index 1ede1e95..3e5a1ae7 100644
--- a/doc/example-dist/binding-checkboxes/objects-matcher/app.html
+++ b/doc/example-dist/binding-checkboxes/objects-matcher/app.html
@@ -11,13 +11,13 @@ <h4>Products</h4>
       <input type="checkbox" model.bind="{ id: 1, name: 'CPU' }"
              matcher.bind="productMatcher"
              checked.bind="selectedProducts">
-      Motherboard
+      CPU
     </label>
     <label>
       <input type="checkbox" model.bind="{ id: 2, name: 'Memory' }"
              matcher.bind="productMatcher"
              checked.bind="selectedProducts">
-      Motherboard
+      Memory
     </label>
 
     Selected products:
diff --git a/doc/example-dist/binding-radios/objects-matcher/app.html b/doc/example-dist/binding-radios/objects-matcher/app.html
index 05d81faa..42d10370 100644
--- a/doc/example-dist/binding-radios/objects-matcher/app.html
+++ b/doc/example-dist/binding-radios/objects-matcher/app.html
@@ -13,14 +13,14 @@ <h4>Products</h4>
              model.bind="{ id: 1, name: 'CPU' }"
              matcher.bind="productMatcher"
              checked.bind="selectedProduct">
-      Motherboard
+      CPU
     </label>
     <label>
       <input type="radio" name="objects-matcher"
              model.bind="{ id: 2, name: 'Memory' }"
              matcher.bind="productMatcher"
              checked.bind="selectedProduct">
-      Motherboard
+      Memory
     </label>
 
     Selected product: ${selectedProduct.id} - ${selectedProduct.name}
diff --git a/package.json b/package.json
index 65965aaa..f0972832 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "aurelia-binding",
-  "version": "1.0.6",
+  "version": "1.0.7",
   "description": "A modern databinding library for JavaScript and HTML.",
   "keywords": [
     "aurelia",