diff --git a/google_glog.props b/google_glog.props
index 0f01c30815..e8650faaa5 100644
--- a/google_glog.props
+++ b/google_glog.props
@@ -14,6 +14,7 @@
   <ItemGroup />
   <Target Name="CopyGlogDll" AfterTargets="Build">
     <Copy SourceFiles="$(SolutionDir)..\Google\glog\$(PrincipiaDependencyConfiguration)\$(Platform)\libglog.dll"
-          DestinationFolder="$(OutDir)"/>
+          DestinationFolder="$(OutDir)"
+          SkipUnchangedFiles="true"/>
   </Target>
 </Project>
\ No newline at end of file
diff --git a/google_protobuf.props b/google_protobuf.props
index ef80e0baed..1a55bed5af 100644
--- a/google_protobuf.props
+++ b/google_protobuf.props
@@ -16,6 +16,7 @@
   <ItemGroup />
   <Target Name="CopyProtobufDll" AfterTargets="Build">
     <Copy SourceFiles="$(SolutionDir)..\Google\protobuf\vsprojects\$(PrincipiaDependencyConfiguration)\$(Platform)\libprotobuf.dll"
-          DestinationFolder="$(OutDir)"/>
+          DestinationFolder="$(OutDir)"
+          SkipUnchangedFiles="true"/>
   </Target>
 </Project>
\ No newline at end of file