diff --git a/Source/NotifyIconWpf/NotifyIconWpf.csproj b/Source/NotifyIconWpf/NotifyIconWpf.csproj
index 4c7b60b..82c3ecf 100644
--- a/Source/NotifyIconWpf/NotifyIconWpf.csproj
+++ b/Source/NotifyIconWpf/NotifyIconWpf.csproj
@@ -39,9 +39,6 @@
   </PropertyGroup>
   <ItemGroup>
     <Reference Include="System" />
-    <Reference Include="System.Core">
-      <RequiredTargetFramework>3.5</RequiredTargetFramework>
-    </Reference>
     <Reference Include="System.Drawing" />
     <Reference Include="System.Xaml" />
     <Reference Include="WindowsBase" />