diff --git a/src/SourceBuild/tarball/content/repos/format.proj b/src/SourceBuild/tarball/content/repos/format.proj
index 21734d18d..59cd432ce 100644
--- a/src/SourceBuild/tarball/content/repos/format.proj
+++ b/src/SourceBuild/tarball/content/repos/format.proj
@@ -9,6 +9,20 @@
     <OutputPlacementRepoApiImplemented>false</OutputPlacementRepoApiImplemented>
   </PropertyGroup>
 
+  <ItemGroup>
+    <!--
+      dotnet/format has a single property MicrosoftExtensionsVersion that controls the version of
+      all packages like 'Microsoft.Extensions.*'. But, there is no package called
+      "Microsoft.Extensions", so the source-built version isn't used and dotnet/format downloads an
+      old version that comes from SBRP and fails at runtime, when you try to use dotnet-format.
+
+      Pick an arbitrary representative package to pass in as MicrosoftExtensionsVersion so it uses
+      the source-built version from the PVP.
+    -->
+    <ExtraPackageVersionPropsPackageInfo Include="MicrosoftExtensionsVersion" Version="%24(MicrosoftExtensionsDependencyInjectionVersion)" />
+  </ItemGroup>
+
+
   <ItemGroup>
     <RepositoryReference Include="roslyn" />
     <RepositoryReference Include="roslyn-analyzers" />