diff --git a/GUIs.ZooFlow/ZooFlow.vbproj b/GUIs.ZooFlow/ZooFlow.vbproj
index 282da679..b83cdd79 100644
--- a/GUIs.ZooFlow/ZooFlow.vbproj
+++ b/GUIs.ZooFlow/ZooFlow.vbproj
@@ -116,7 +116,9 @@
     </Reference>
     <Reference Include="PresentationCore" />
     <Reference Include="PresentationFramework" />
-    <Reference Include="System" />
+    <Reference Include="System">
+      <HintPath>C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.6.1\System.dll</HintPath>
+    </Reference>
     <Reference Include="System.ComponentModel.DataAnnotations" />
     <Reference Include="System.Configuration" />
     <Reference Include="System.Core" />