diff --git a/Octokit.nuspec b/Octokit.nuspec
index cc5a8175..03d9c88b 100644
--- a/Octokit.nuspec
+++ b/Octokit.nuspec
@@ -26,6 +26,7 @@
       </group>
     </dependencies>
     <frameworkAssemblies>
+      <frameworkAssembly assemblyName="System" targetFramework="net45" />
       <frameworkAssembly assemblyName="System.Net.Http" targetFramework="net45, netcore45" />
     </frameworkAssemblies>
   </metadata>