diff --git a/ThScoreFileConverter/ThScoreFileConverter.csproj b/ThScoreFileConverter/ThScoreFileConverter.csproj
index 581a6a75..6bc10dc7 100644
--- a/ThScoreFileConverter/ThScoreFileConverter.csproj
+++ b/ThScoreFileConverter/ThScoreFileConverter.csproj
@@ -77,7 +77,7 @@
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetFramework)' == 'net48'">
-    <PackageReference Include="System.Collections.Immutable" Version="7.0.0" />
+    <PackageReference Include="System.Collections.Immutable" Version="8.0.0" />
     <PackageReference Include="System.Text.Encoding.CodePages" Version="8.0.0" />
   </ItemGroup>