diff --git a/src/BuiltInTools/DotNetDeltaApplier/Microsoft.Extensions.DotNetDeltaApplier.csproj b/src/BuiltInTools/DotNetDeltaApplier/Microsoft.Extensions.DotNetDeltaApplier.csproj
index 00077513c7e4..fa302f742787 100644
--- a/src/BuiltInTools/DotNetDeltaApplier/Microsoft.Extensions.DotNetDeltaApplier.csproj
+++ b/src/BuiltInTools/DotNetDeltaApplier/Microsoft.Extensions.DotNetDeltaApplier.csproj
@@ -10,6 +10,12 @@
       and HotReloadAppModel.TryGetStartupHookPath.
     -->
     <TargetFrameworks>net6.0;net10.0</TargetFrameworks>
+
+    <!--
+      Set version of Microsoft.NETCore.App.Ref to one that's available in source build.
+    -->
+    <TargetingPackVersion Condition="'$(TargetFramework)' == 'net6.0' and '$(DotNetBuildSourceOnly)' == 'true'">6.0.0</TargetingPackVersion>
+
     <StrongNameKeyId>MicrosoftAspNetCore</StrongNameKeyId>
 
     <!-- NuGet -->
diff --git a/src/BuiltInTools/HotReloadAgent/Microsoft.DotNet.HotReload.Agent.Package.csproj b/src/BuiltInTools/HotReloadAgent/Microsoft.DotNet.HotReload.Agent.Package.csproj
index b56c85d86597..bd92efbdfbff 100644
--- a/src/BuiltInTools/HotReloadAgent/Microsoft.DotNet.HotReload.Agent.Package.csproj
+++ b/src/BuiltInTools/HotReloadAgent/Microsoft.DotNet.HotReload.Agent.Package.csproj
@@ -4,6 +4,12 @@
       Intentionally pinned. This feature is supported in projects targeting 6.0 or newer.
     -->
     <TargetFramework>net6.0</TargetFramework>
+
+    <!--
+      Set version of Microsoft.NETCore.App.Ref to one that's available in source build.
+    -->
+    <TargetingPackVersion Condition="'$(DotNetBuildSourceOnly)' == 'true'">6.0.0</TargetingPackVersion>
+
     <GenerateDocumentationFile>false</GenerateDocumentationFile>
     <DebugType>none</DebugType>
     <GenerateDependencyFile>false</GenerateDependencyFile>