diff --git a/build/NuSpecs/UmbracoCms.Core.nuspec b/build/NuSpecs/UmbracoCms.Core.nuspec
index dbc7be00e4..450aec09b6 100644
--- a/build/NuSpecs/UmbracoCms.Core.nuspec
+++ b/build/NuSpecs/UmbracoCms.Core.nuspec
@@ -30,7 +30,7 @@
       <dependency id="ClientDependency" version="[1.9.1, 2.0.0)" />
       <dependency id="ClientDependency-Mvc5" version="[1.8.0, 2.0.0)" />
 	  <!-- AutoMapper can not be updated due to: https://github.com/AutoMapper/AutoMapper/issues/373#issuecomment-127644405 -->
-      <dependency id="AutoMapper" version="[3.0.0, 3.1.0)" />
+      <dependency id="AutoMapper" version="[3.3.1, 4.0.0)" />
       <dependency id="Newtonsoft.Json" version="[6.0.8, 10.0.0)" />
       <dependency id="Examine" version="[0.1.69, 1.0.0)" />
       <dependency id="ImageProcessor" version="[2.4.4, 3.0.0)" />
diff --git a/build/NuSpecs/tools/Web.config.install.xdt b/build/NuSpecs/tools/Web.config.install.xdt
index 987db6c3d6..2d5dfb0bdb 100644
--- a/build/NuSpecs/tools/Web.config.install.xdt
+++ b/build/NuSpecs/tools/Web.config.install.xdt
@@ -319,6 +319,7 @@
   <runtime>
     <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
       <dependentAssembly xdt:Locator="Condition(./_defaultNamespace:assemblyIdentity/@name='HtmlAgilityPack')" xdt:Transform="Remove" />
+      <dependentAssembly xdt:Locator="Condition(./_defaultNamespace:assemblyIdentity/@name='AutoMapper')" xdt:Transform="Remove" />
       <dependentAssembly xdt:Locator="Condition(./_defaultNamespace:assemblyIdentity/@name='System.Net.Http')" xdt:Transform="Remove" />
       <dependentAssembly xdt:Locator="Condition(./_defaultNamespace:assemblyIdentity/@name='Newtonsoft.Json')" xdt:Transform="Remove" />
       <dependentAssembly xdt:Locator="Condition(./_defaultNamespace:assemblyIdentity/@name='System.Web.Mvc')" xdt:Transform="Remove" />
@@ -338,6 +339,10 @@
         <assemblyIdentity name="HtmlAgilityPack" publicKeyToken="bd319b19eaf3b43a" culture="neutral" />
         <bindingRedirect oldVersion="0.0.0.0-1.4.9.0" newVersion="1.4.9.0" />
       </dependentAssembly>
+      <dependentAssembly xdt:Transform="Insert">
+        <assemblyIdentity name="AutoMapper" publicKeyToken="be96cd2c38ef1005" culture="neutral" />
+        <bindingRedirect oldVersion="0.0.0.0-3.3.1.0" newVersion="3.3.1.0" />
+      </dependentAssembly>
       <dependentAssembly xdt:Transform="Insert">
         <assemblyIdentity name="System.Net.Http" publicKeyToken="b03f5f7f11d50a3a" culture="neutral"/>
         <bindingRedirect oldVersion="0.0.0.0-4.0.0.0" newVersion="4.0.0.0"/>
diff --git a/build/UmbracoVersion.txt b/build/UmbracoVersion.txt
index df444cdd7b..469bf7a466 100644
--- a/build/UmbracoVersion.txt
+++ b/build/UmbracoVersion.txt
@@ -1,2 +1,2 @@
 # Usage: on line 2 put the release version, on line 3 put the version comment (example: beta)
-7.5.3
\ No newline at end of file
+7.5.4
\ No newline at end of file
diff --git a/src/Umbraco.Core/IO/UmbracoMediaFile.cs b/src/Umbraco.Core/IO/UmbracoMediaFile.cs
index b168ce89b4..8e1d8c0987 100644
--- a/src/Umbraco.Core/IO/UmbracoMediaFile.cs
+++ b/src/Umbraco.Core/IO/UmbracoMediaFile.cs
@@ -80,8 +80,9 @@ namespace Umbraco.Core.IO
         private void Initialize()
         {
             Filename = _fs.GetFileName(Path);
-            Extension = _fs.GetExtension(Path) != null
-                ? _fs.GetExtension(Path).TrimStart('.').ToLowerInvariant()
+            var ext = _fs.GetExtension(Path);
+            Extension = string.IsNullOrEmpty(ext) == false
+                ? ext.TrimStart('.').ToLowerInvariant()
                 : "";
             Url = _fs.GetUrl(Path);
 
diff --git a/src/Umbraco.Core/Umbraco.Core.csproj b/src/Umbraco.Core/Umbraco.Core.csproj
index 78e0cdc632..91ce68b8af 100644
--- a/src/Umbraco.Core/Umbraco.Core.csproj
+++ b/src/Umbraco.Core/Umbraco.Core.csproj
@@ -37,12 +37,12 @@
     <Prefer32Bit>false</Prefer32Bit>
   </PropertyGroup>
   <ItemGroup>
-    <Reference Include="AutoMapper, Version=3.0.0.0, Culture=neutral, processorArchitecture=MSIL">
-      <HintPath>..\packages\AutoMapper.3.0.0\lib\net40\AutoMapper.dll</HintPath>
+    <Reference Include="AutoMapper, Version=3.3.1.0, Culture=neutral, PublicKeyToken=be96cd2c38ef1005, processorArchitecture=MSIL">
+      <HintPath>..\packages\AutoMapper.3.3.1\lib\net40\AutoMapper.dll</HintPath>
       <Private>True</Private>
     </Reference>
-    <Reference Include="AutoMapper.Net4, Version=0.0.0.0, Culture=neutral, processorArchitecture=MSIL">
-      <HintPath>..\packages\AutoMapper.3.0.0\lib\net40\AutoMapper.Net4.dll</HintPath>
+    <Reference Include="AutoMapper.Net4, Version=3.3.1.0, Culture=neutral, PublicKeyToken=be96cd2c38ef1005, processorArchitecture=MSIL">
+      <HintPath>..\packages\AutoMapper.3.3.1\lib\net40\AutoMapper.Net4.dll</HintPath>
       <Private>True</Private>
     </Reference>
     <Reference Include="HtmlAgilityPack, Version=1.4.9.0, Culture=neutral, PublicKeyToken=bd319b19eaf3b43a, processorArchitecture=MSIL">
@@ -1461,6 +1461,7 @@
   </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <Import Project="$(SolutionDir)\.nuget\nuget.targets" />
+  <Import Project="..\packages\AutoMapper.3.3.1\tools\AutoMapper.targets" Condition="Exists('..\packages\AutoMapper.3.3.1\tools\AutoMapper.targets')" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
        Other similar extension points exist, see Microsoft.Common.targets.
   <Target Name="BeforeBuild">
diff --git a/src/Umbraco.Core/UmbracoApplicationBase.cs b/src/Umbraco.Core/UmbracoApplicationBase.cs
index bb81c79f2a..e4574a7972 100644
--- a/src/Umbraco.Core/UmbracoApplicationBase.cs
+++ b/src/Umbraco.Core/UmbracoApplicationBase.cs
@@ -48,6 +48,9 @@ namespace Umbraco.Core
                 LogHelper.Error<UmbracoApplicationBase>(msg, exception);
             };
 
+            // this only gets called when an assembly can't be resolved
+            AppDomain.CurrentDomain.AssemblyResolve += CurrentDomainOnAssemblyResolve;
+
             //boot up the application
             GetBootManager()
                 .Initialize()
@@ -58,6 +61,22 @@ namespace Umbraco.Core
             ApplicationEventsResolver.Current.Dispose();
         }
 
+        /// <summary>
+        /// Called when an assembly can't be resolved. In here we can do magic with the assembly name and try loading another.
+        /// This is used for loading a signed assembly of AutoMapper (v. 3.1+) without having to recompile old code.
+        /// </summary>
+        /// <param name="sender"></param>
+        /// <param name="args"></param>
+        /// <returns></returns>
+        private Assembly CurrentDomainOnAssemblyResolve(object sender, ResolveEventArgs args)
+        {
+            // ensure the assembly is indeed AutoMapper and that the PublicKeyToken is null before trying to Load again
+            // do NOT just replace this with 'return Assembly', as it will cause an infinite loop -> stackoverflow
+            if (args.Name.StartsWith("AutoMapper") && args.Name.EndsWith("PublicKeyToken=null"))
+                return Assembly.Load(args.Name.Replace(", PublicKeyToken=null", ", PublicKeyToken=be96cd2c38ef1005"));
+            return null;
+        }
+
         /// <summary>
         /// Initializes the Umbraco application
         /// </summary>
diff --git a/src/Umbraco.Core/packages.config b/src/Umbraco.Core/packages.config
index 155fead690..ff80fe795c 100644
--- a/src/Umbraco.Core/packages.config
+++ b/src/Umbraco.Core/packages.config
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <packages>
-  <package id="AutoMapper" version="3.0.0" targetFramework="net45" />
+  <package id="AutoMapper" version="3.3.1" targetFramework="net45" />
   <package id="HtmlAgilityPack" version="1.4.9" targetFramework="net45" />
   <package id="ImageProcessor" version="2.4.4.0" targetFramework="net45" />
   <package id="log4net-mediumtrust" version="2.0.0" targetFramework="net4" />
diff --git a/src/Umbraco.Tests/Umbraco.Tests.csproj b/src/Umbraco.Tests/Umbraco.Tests.csproj
index d5f33151f4..041a11836c 100644
--- a/src/Umbraco.Tests/Umbraco.Tests.csproj
+++ b/src/Umbraco.Tests/Umbraco.Tests.csproj
@@ -51,12 +51,12 @@
     <Prefer32Bit>false</Prefer32Bit>
   </PropertyGroup>
   <ItemGroup>
-    <Reference Include="AutoMapper, Version=3.0.0.0, Culture=neutral, processorArchitecture=MSIL">
-      <HintPath>..\packages\AutoMapper.3.0.0\lib\net40\AutoMapper.dll</HintPath>
+    <Reference Include="AutoMapper, Version=3.3.1.0, Culture=neutral, PublicKeyToken=be96cd2c38ef1005, processorArchitecture=MSIL">
+      <HintPath>..\packages\AutoMapper.3.3.1\lib\net40\AutoMapper.dll</HintPath>
       <Private>True</Private>
     </Reference>
-    <Reference Include="AutoMapper.Net4, Version=0.0.0.0, Culture=neutral, processorArchitecture=MSIL">
-      <HintPath>..\packages\AutoMapper.3.0.0\lib\net40\AutoMapper.Net4.dll</HintPath>
+    <Reference Include="AutoMapper.Net4, Version=3.3.1.0, Culture=neutral, PublicKeyToken=be96cd2c38ef1005, processorArchitecture=MSIL">
+      <HintPath>..\packages\AutoMapper.3.3.1\lib\net40\AutoMapper.Net4.dll</HintPath>
       <Private>True</Private>
     </Reference>
     <Reference Include="Examine, Version=0.1.69.0, Culture=neutral, processorArchitecture=MSIL">
@@ -767,6 +767,7 @@
 xcopy "$(ProjectDir)"..\packages\SqlServerCE.4.0.0.1\x86\*.* "$(TargetDir)x86\" /Y /F /E /I /C /D</PreBuildEvent>
   </PropertyGroup>
   <Import Project="$(SolutionDir)\.nuget\nuget.targets" />
+  <Import Project="..\packages\AutoMapper.3.3.1\tools\AutoMapper.targets" Condition="Exists('..\packages\AutoMapper.3.3.1\tools\AutoMapper.targets')" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it.
        Other similar extension points exist, see Microsoft.Common.targets.
   <Target Name="BeforeBuild">
diff --git a/src/Umbraco.Tests/packages.config b/src/Umbraco.Tests/packages.config
index cc0fc5f214..4cd43feb35 100644
--- a/src/Umbraco.Tests/packages.config
+++ b/src/Umbraco.Tests/packages.config
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <packages>
   <package id="AspNetWebApi.SelfHost" version="4.0.20710.0" targetFramework="net45" />
-  <package id="AutoMapper" version="3.0.0" targetFramework="net45" />
+  <package id="AutoMapper" version="3.3.1" targetFramework="net45" />
   <package id="Examine" version="0.1.69.0" targetFramework="net45" />
   <package id="log4net-mediumtrust" version="2.0.0" targetFramework="net45" />
   <package id="Lucene.Net" version="2.9.4.1" targetFramework="net45" />
diff --git a/src/Umbraco.Web.UI/Umbraco.Web.UI.csproj b/src/Umbraco.Web.UI/Umbraco.Web.UI.csproj
index 85aff6e9cf..2f26215b42 100644
--- a/src/Umbraco.Web.UI/Umbraco.Web.UI.csproj
+++ b/src/Umbraco.Web.UI/Umbraco.Web.UI.csproj
@@ -107,12 +107,12 @@
       <Project>{07fbc26b-2927-4a22-8d96-d644c667fecc}</Project>
       <Name>UmbracoExamine</Name>
     </ProjectReference>
-    <Reference Include="AutoMapper, Version=3.0.0.0, Culture=neutral, processorArchitecture=MSIL">
-      <HintPath>..\packages\AutoMapper.3.0.0\lib\net40\AutoMapper.dll</HintPath>
+    <Reference Include="AutoMapper, Version=3.3.1.0, Culture=neutral, PublicKeyToken=be96cd2c38ef1005, processorArchitecture=MSIL">
+      <HintPath>..\packages\AutoMapper.3.3.1\lib\net40\AutoMapper.dll</HintPath>
       <Private>True</Private>
     </Reference>
-    <Reference Include="AutoMapper.Net4, Version=0.0.0.0, Culture=neutral, processorArchitecture=MSIL">
-      <HintPath>..\packages\AutoMapper.3.0.0\lib\net40\AutoMapper.Net4.dll</HintPath>
+    <Reference Include="AutoMapper.Net4, Version=3.3.1.0, Culture=neutral, PublicKeyToken=be96cd2c38ef1005, processorArchitecture=MSIL">
+      <HintPath>..\packages\AutoMapper.3.3.1\lib\net40\AutoMapper.Net4.dll</HintPath>
       <Private>True</Private>
     </Reference>
     <Reference Include="ClientDependency.Core, Version=1.9.1.0, Culture=neutral, processorArchitecture=MSIL">
@@ -2453,4 +2453,5 @@ xcopy "$(ProjectDir)"..\packages\SqlServerCE.4.0.0.1\x86\*.* "$(TargetDir)x86\"
     </ReadLinesFromFile>
     <Exec WorkingDirectory="$(ProjectDir)\..\..\build\" Command="BuildBelle.bat $(VersionNumber)" ConsoleToMSBuild="true" IgnoreExitCode="true" ContinueOnError="WarnAndContinue" />
   </Target>
+  <Import Project="..\packages\AutoMapper.3.3.1\tools\AutoMapper.targets" Condition="Exists('..\packages\AutoMapper.3.3.1\tools\AutoMapper.targets')" />
 </Project>
\ No newline at end of file
diff --git a/src/Umbraco.Web.UI/packages.config b/src/Umbraco.Web.UI/packages.config
index 9603b6eac8..d1b2e59a19 100644
--- a/src/Umbraco.Web.UI/packages.config
+++ b/src/Umbraco.Web.UI/packages.config
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <packages>
-  <package id="AutoMapper" version="3.0.0" targetFramework="net45" />
+  <package id="AutoMapper" version="3.3.1" targetFramework="net45" />
   <package id="ClientDependency" version="1.9.1" targetFramework="net45" />
   <package id="ClientDependency-Mvc5" version="1.8.0.0" targetFramework="net45" />
   <package id="dotless" version="1.4.1.0" targetFramework="net45" />
diff --git a/src/Umbraco.Web.UI/web.Template.config b/src/Umbraco.Web.UI/web.Template.config
index ffc8889625..ec7948a09a 100644
--- a/src/Umbraco.Web.UI/web.Template.config
+++ b/src/Umbraco.Web.UI/web.Template.config
@@ -381,6 +381,11 @@
 				<bindingRedirect oldVersion="0.0.0.0-4.0.0.0" newVersion="4.0.0.0"/>
 			</dependentAssembly>
 
+      <dependentAssembly>
+        <assemblyIdentity name="AutoMapper" publicKeyToken="be96cd2c38ef1005" culture="neutral" />
+        <bindingRedirect oldVersion="0.0.0.0-3.3.1.0" newVersion="3.3.1.0" />
+      </dependentAssembly>
+      
 			<dependentAssembly>
 				<assemblyIdentity name="Newtonsoft.Json" publicKeyToken="30ad4fe6b2a6aeed" culture="neutral" />
 				<bindingRedirect oldVersion="0.0.0.0-6.0.0.0" newVersion="6.0.0.0" />
diff --git a/src/Umbraco.Web/Umbraco.Web.csproj b/src/Umbraco.Web/Umbraco.Web.csproj
index 400b6d65e0..c89e60a399 100644
--- a/src/Umbraco.Web/Umbraco.Web.csproj
+++ b/src/Umbraco.Web/Umbraco.Web.csproj
@@ -97,14 +97,12 @@
       <Project>{07fbc26b-2927-4a22-8d96-d644c667fecc}</Project>
       <Name>UmbracoExamine</Name>
     </ProjectReference>
-    <Reference Include="AutoMapper, Version=3.0.0.0, Culture=neutral, processorArchitecture=MSIL">
-      <HintPath>..\packages\AutoMapper.3.0.0\lib\net40\AutoMapper.dll</HintPath>
-      <SpecificVersion>False</SpecificVersion>
+    <Reference Include="AutoMapper, Version=3.3.1.0, Culture=neutral, PublicKeyToken=be96cd2c38ef1005, processorArchitecture=MSIL">
+      <HintPath>..\packages\AutoMapper.3.3.1\lib\net40\AutoMapper.dll</HintPath>
       <Private>True</Private>
     </Reference>
-    <Reference Include="AutoMapper.Net4, Version=0.0.0.0, Culture=neutral, processorArchitecture=MSIL">
-      <HintPath>..\packages\AutoMapper.3.0.0\lib\net40\AutoMapper.Net4.dll</HintPath>
-      <SpecificVersion>False</SpecificVersion>
+    <Reference Include="AutoMapper.Net4, Version=3.3.1.0, Culture=neutral, PublicKeyToken=be96cd2c38ef1005, processorArchitecture=MSIL">
+      <HintPath>..\packages\AutoMapper.3.3.1\lib\net40\AutoMapper.Net4.dll</HintPath>
       <Private>True</Private>
     </Reference>
     <Reference Include="ClientDependency.Core, Version=1.9.1.0, Culture=neutral, processorArchitecture=MSIL">
@@ -2269,4 +2267,5 @@
     <!--<PostBuildEvent>xcopy "$(ProjectDir)..\..\lib\*.dll" "$(TargetDir)*.dll" /Y</PostBuildEvent>-->
   </PropertyGroup>
   <Import Project="$(SolutionDir)\.nuget\nuget.targets" />
+  <Import Project="..\packages\AutoMapper.3.3.1\tools\AutoMapper.targets" Condition="Exists('..\packages\AutoMapper.3.3.1\tools\AutoMapper.targets')" />
 </Project>
\ No newline at end of file
diff --git a/src/Umbraco.Web/packages.config b/src/Umbraco.Web/packages.config
index b0668a9210..9106e59fe0 100644
--- a/src/Umbraco.Web/packages.config
+++ b/src/Umbraco.Web/packages.config
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <packages>
-  <package id="AutoMapper" version="3.0.0" targetFramework="net45" />
+  <package id="AutoMapper" version="3.3.1" targetFramework="net45" />
   <package id="ClientDependency" version="1.9.1" targetFramework="net45" />
   <package id="dotless" version="1.4.1.0" targetFramework="net45" />
   <package id="Examine" version="0.1.69.0" targetFramework="net45" />
diff --git a/src/umbraco.businesslogic/packages.config b/src/umbraco.businesslogic/packages.config
index 4a0a1d249b..65ef682839 100644
--- a/src/umbraco.businesslogic/packages.config
+++ b/src/umbraco.businesslogic/packages.config
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <packages>
-  <package id="AutoMapper" version="3.0.0" targetFramework="net45" />
+  <package id="AutoMapper" version="3.3.1" targetFramework="net45" />
   <package id="Microsoft.AspNet.Mvc" version="5.2.3" targetFramework="net45" />
   <package id="Microsoft.AspNet.Razor" version="3.2.3" targetFramework="net45" />
   <package id="Microsoft.AspNet.WebPages" version="3.2.3" targetFramework="net45" />
diff --git a/src/umbraco.businesslogic/umbraco.businesslogic.csproj b/src/umbraco.businesslogic/umbraco.businesslogic.csproj
index e134c33eab..1483523caf 100644
--- a/src/umbraco.businesslogic/umbraco.businesslogic.csproj
+++ b/src/umbraco.businesslogic/umbraco.businesslogic.csproj
@@ -106,12 +106,12 @@
     <Prefer32Bit>false</Prefer32Bit>
   </PropertyGroup>
   <ItemGroup>
-    <Reference Include="AutoMapper, Version=3.0.0.0, Culture=neutral, processorArchitecture=MSIL">
-      <HintPath>..\packages\AutoMapper.3.0.0\lib\net40\AutoMapper.dll</HintPath>
+    <Reference Include="AutoMapper, Version=3.3.1.0, Culture=neutral, PublicKeyToken=be96cd2c38ef1005, processorArchitecture=MSIL">
+      <HintPath>..\packages\AutoMapper.3.3.1\lib\net40\AutoMapper.dll</HintPath>
       <Private>True</Private>
     </Reference>
-    <Reference Include="AutoMapper.Net4, Version=0.0.0.0, Culture=neutral, processorArchitecture=MSIL">
-      <HintPath>..\packages\AutoMapper.3.0.0\lib\net40\AutoMapper.Net4.dll</HintPath>
+    <Reference Include="AutoMapper.Net4, Version=3.3.1.0, Culture=neutral, PublicKeyToken=be96cd2c38ef1005, processorArchitecture=MSIL">
+      <HintPath>..\packages\AutoMapper.3.3.1\lib\net40\AutoMapper.Net4.dll</HintPath>
       <Private>True</Private>
     </Reference>
     <Reference Include="Microsoft.Owin, Version=3.0.1.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35, processorArchitecture=MSIL">
@@ -295,4 +295,5 @@
     </PostBuildEvent>
   </PropertyGroup>
   <Import Project="$(SolutionDir)\.nuget\nuget.targets" />
+  <Import Project="..\packages\AutoMapper.3.3.1\tools\AutoMapper.targets" Condition="Exists('..\packages\AutoMapper.3.3.1\tools\AutoMapper.targets')" />
 </Project>
\ No newline at end of file