diff --git a/Directory.Build.props b/Directory.Build.props
index 84b1730184..d696002cb8 100644
--- a/Directory.Build.props
+++ b/Directory.Build.props
@@ -1,6 +1,7 @@
 <Project>
   <Import Project="version.props" />
   <Import Project="build\dependencies.props" />
+  <Import Project="build\sources.props" />
 
  <PropertyGroup>
     <Product>Microsoft ASP.NET Core</Product>
@@ -10,4 +11,4 @@
     <SignAssembly>true</SignAssembly>
     <PublicSign Condition="'$(OS)' != 'Windows_NT'">true</PublicSign>
   </PropertyGroup>
-</Project>
\ No newline at end of file
+</Project>
diff --git a/NuGet.config b/NuGet.config
index f495268808..e32bddfd51 100644
--- a/NuGet.config
+++ b/NuGet.config
@@ -2,8 +2,6 @@
 <configuration>
   <packageSources>
     <clear />
-    <add key="AspNetCore" value="https://dotnet.myget.org/F/aspnetcore-ci-dev/api/v3/index.json" />
-    <add key="AspNetCoreTools" value="https://dotnet.myget.org/F/aspnetcore-tools/api/v3/index.json" />
-    <add key="NuGet" value="https://api.nuget.org/v3/index.json" />
+    <!-- Restore sources should be defined in build/sources.props. -->
   </packageSources>
-</configuration>
\ No newline at end of file
+</configuration>
diff --git a/build/dependencies.props b/build/dependencies.props
index 3524f8edcb..0fc2c94e6c 100644
--- a/build/dependencies.props
+++ b/build/dependencies.props
@@ -5,7 +5,7 @@
   <PropertyGroup Label="Package Versions">
     <InternalAspNetCoreSdkPackageVersion>2.1.0-preview1-15549</InternalAspNetCoreSdkPackageVersion>
     <MicrosoftAspNetCoreAllPackageVersion>2.0.0</MicrosoftAspNetCoreAllPackageVersion>
-    <MicrosoftAspNetCoreTestingPackageVersion>2.1.0-preview1-27424</MicrosoftAspNetCoreTestingPackageVersion>
+    <MicrosoftAspNetCoreTestingPackageVersion>2.1.0-preview1-27644</MicrosoftAspNetCoreTestingPackageVersion>
     <MicrosoftExtensionsLoggingConsolePackageVersion>2.0.0</MicrosoftExtensionsLoggingConsolePackageVersion>
     <MicrosoftExtensionsLoggingDebugPackageVersion>2.0.0</MicrosoftExtensionsLoggingDebugPackageVersion>
     <MicrosoftExtensionsLoggingPackageVersion>2.0.0</MicrosoftExtensionsLoggingPackageVersion>
diff --git a/build/repo.props b/build/repo.props
index 9df3355343..0969ca492d 100644
--- a/build/repo.props
+++ b/build/repo.props
@@ -12,6 +12,6 @@
   <PropertyGroup>
     <!-- These properties are use by the automation that updates dependencies.props -->
     <LineupPackageId>Internal.AspNetCore.Universe.Lineup</LineupPackageId>
-    <LineupPackageRestoreSource>https://dotnet.myget.org/F/aspnetcore-ci-dev/api/v3/index.json</LineupPackageRestoreSource>
+    <LineupPackageRestoreSource>https://dotnet.myget.org/F/aspnetcore-dev/api/v3/index.json</LineupPackageRestoreSource>
   </PropertyGroup>
 </Project>
diff --git a/build/sources.props b/build/sources.props
new file mode 100644
index 0000000000..05a4b7dc2e
--- /dev/null
+++ b/build/sources.props
@@ -0,0 +1,16 @@
+<Project>
+  <Import Project="$(DotNetRestoreSourcePropsPath)" Condition="'$(DotNetRestoreSourcePropsPath)' != ''"/>
+
+  <PropertyGroup Label="RestoreSources">
+    <RestoreSources>$(DotNetRestoreSources)</RestoreSources>
+    <RestoreSources Condition="'$(DotNetBuildOffline)' != 'true' AND '$(AspNetUniverseBuildOffline)' != 'true' ">
+      $(RestoreSources);
+      https://dotnet.myget.org/F/aspnetcore-dev/api/v3/index.json;
+      https://dotnet.myget.org/F/aspnetcore-tools/api/v3/index.json;
+    </RestoreSources>
+    <RestoreSources Condition="'$(DotNetBuildOffline)' != 'true'">
+      $(RestoreSources);
+      https://api.nuget.org/v3/index.json;
+    </RestoreSources>
+  </PropertyGroup>
+</Project>
diff --git a/korebuild-lock.txt b/korebuild-lock.txt
index 5f7f568497..fe4a961da3 100644
--- a/korebuild-lock.txt
+++ b/korebuild-lock.txt
@@ -1,2 +1,2 @@
-version:2.1.0-preview1-15555
-commithash:97b60e251fce2680a08866ab977aa7e3b4f92b86
+version:2.1.0-preview1-15620
+commithash:6432b49a2c00310416df39b6fe548ef4af9c6011