diff --git a/Directory.Packages.props b/Directory.Packages.props
index f1a289a..ba14ce6 100644
--- a/Directory.Packages.props
+++ b/Directory.Packages.props
@@ -50,7 +50,7 @@
       CentralPackageTransitivePinningEnabled promotes this central version everywhere, including
       projects that never reference the package directly.
     -->
-    <PackageVersion Include="System.Collections.Immutable" Version="10.0.12" />
+    <PackageVersion Include="System.Collections.Immutable" Version="10.0.15" />
   </ItemGroup>
   <ItemGroup Label="Testing">
     <PackageVersion Include="Microsoft.Testing.Extensions.CodeCoverage" Version="18.12.0" />
diff --git a/src/NetEvolve.FrameShift/NetEvolve.FrameShift.Roslyn4_8.csproj b/src/NetEvolve.FrameShift/NetEvolve.FrameShift.Roslyn4_8.csproj
index 232a6ac..c0b61bd 100644
--- a/src/NetEvolve.FrameShift/NetEvolve.FrameShift.Roslyn4_8.csproj
+++ b/src/NetEvolve.FrameShift/NetEvolve.FrameShift.Roslyn4_8.csproj
@@ -47,7 +47,7 @@
       variant's own need) - because a net6.0/net7.0 test project referencing this variant would otherwise
       inherit a version its own reference assemblies don't agree with.
     -->
-    <PackageReference Include="System.Collections.Immutable" PrivateAssets="all" VersionOverride="10.0.12" />
+    <PackageReference Include="System.Collections.Immutable" PrivateAssets="all" VersionOverride="10.0.15" />
   </ItemGroup>
 
   <Import Project="Sdk.targets" Sdk="Microsoft.NET.Sdk" />