diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9b8fe6a..358474b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,7 @@
 
 * Fixes issue where proxied models created from IContent models did not support recursive hydration.
 * Fixes issue where if a proxy property was overwritten with some value not from CMS, it would not persist and would still use CMS value.
+* Fixes issue where preview content breaks due to use of a singleton UmbracoHelper. [#34]
 
 ## v1.3.0
 
diff --git a/ReferenceWebsite/App_Data/Umbraco.sdf b/ReferenceWebsite/App_Data/Umbraco.sdf
index 4be8ce1..6af7c7f 100644
Binary files a/ReferenceWebsite/App_Data/Umbraco.sdf and b/ReferenceWebsite/App_Data/Umbraco.sdf differ
diff --git a/UmbracoVault/Extensions/DictionaryExtensions.cs b/UmbracoVault/Extensions/DictionaryExtensions.cs
new file mode 100644
index 0000000..1adb913
--- /dev/null
+++ b/UmbracoVault/Extensions/DictionaryExtensions.cs
@@ -0,0 +1,42 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace UmbracoVault.Extensions
+{
+    internal static class DictionaryExtensions
+    {
+        public static object GetOrAddThreadSafe(this IDictionary dictionary, object key, Func<object, object> valueFactory)
+        {
+            if (!dictionary.Contains(key))
+            {
+                lock (key)
+                {
+                    if (!dictionary.Contains(key))
+                    {
+                        dictionary.Add(key, valueFactory(key));
+                    }
+                }
+            }
+
+            return dictionary[key];
+        }
+
+        public static object GetOrAddThreadSafe(this IDictionary dictionary, object key, object value)
+        {
+            return dictionary.GetOrAddThreadSafe(key, k => value);
+        }
+
+        public static T GetOrAddThreadSafe<T>(this IDictionary dictionary, object key, Func<object, T> valueFactory)
+        {
+            var factoryWrapper = new Func<object, object>(k => valueFactory(k));
+            return (T)dictionary.GetOrAddThreadSafe(key, factoryWrapper);
+        }
+
+        public static T GetOrAddThreadSafe<T>(this IDictionary dictionary, object key, T value)
+        {
+            return dictionary.GetOrAddThreadSafe(key, k => value);
+        }
+    }
+}
\ No newline at end of file
diff --git a/UmbracoVault/UmbracoContext.cs b/UmbracoVault/UmbracoContext.cs
index 12f6fee..2675939 100644
--- a/UmbracoVault/UmbracoContext.cs
+++ b/UmbracoVault/UmbracoContext.cs
@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.Linq;
+using System.Web;
 
 using Umbraco.Core;
 using Umbraco.Core.Logging;
@@ -28,8 +29,7 @@ public class UmbracoWebContext : BaseUmbracoContext
             //new SuperScriptTransformation()
         };
 
-        private UmbracoHelper _helper;
-        protected UmbracoHelper Helper => _helper ?? (_helper = new UmbracoHelper(UmbracoContext.Current));
+        protected UmbracoHelper Helper => GetUmbracoHelperForRequest();
 
         private IPublishedContent GetCurrentUmbracoContent()
         {
@@ -166,6 +166,12 @@ protected T GetItem<T>(IPublishedContent n)
             return result;
         }
 
+        private static UmbracoHelper GetUmbracoHelperForRequest()
+        {
+            const string umbracoHelperKey = "__vaultUmbracoHelper";
+            return HttpContext.Current?.Items.GetOrAddThreadSafe(string.Intern(umbracoHelperKey), new UmbracoHelper(UmbracoContext.Current));
+        }
+
         public static ReadOnlyCollection<string> GetUmbracoEntityAliasesFromType(Type type)
         {
             var results = new HashSet<string>();
diff --git a/UmbracoVault/UmbracoVault.csproj b/UmbracoVault/UmbracoVault.csproj
index 2597ee8..d8f61a8 100644
--- a/UmbracoVault/UmbracoVault.csproj
+++ b/UmbracoVault/UmbracoVault.csproj
@@ -87,6 +87,7 @@
     <Compile Include="Controllers\VaultDefaultGenericController.cs" />
     <Compile Include="Controllers\VaultRenderMvcController.cs" />
     <Compile Include="Exceptions\VaultNotImplementedException.cs" />
+    <Compile Include="Extensions\DictionaryExtensions.cs" />
     <Compile Include="Extensions\ObjectExtensions.cs" />
     <Compile Include="Models\NamedItem.cs" />
     <Compile Include="Proxy\ILazyResolverMixin.cs" />
diff --git a/UmbracoVault/UmbracoVault.nuspec b/UmbracoVault/UmbracoVault.nuspec
index 2401fc5..32f864f 100644
--- a/UmbracoVault/UmbracoVault.nuspec
+++ b/UmbracoVault/UmbracoVault.nuspec
@@ -14,6 +14,7 @@
         <releaseNotes>
           * Fixes issue where proxied models created from IContent models did not support recursive hydration.
           * Fixes issue where if a proxy property was overwritten with some value not from CMS, it would not persist and would still use CMS value.
+          * Fixes issue where preview content breaks due to use of a singleton UmbracoHelper. [#34]
         </releaseNotes>
       <copyright>(c) The Nerdery LLC 2016. All Rights Reserved.</copyright>
       <tags>Umbraco UmbracoVault Mapping ObjectMapper ORM CMS</tags>