diff --git a/Lib9c/Lib9c.csproj b/Lib9c/Lib9c.csproj
index c21c85d8ac..436ccc3533 100644
--- a/Lib9c/Lib9c.csproj
+++ b/Lib9c/Lib9c.csproj
@@ -21,7 +21,7 @@
 
   <ItemGroup>
     <PackageReference Include="DecimalMath.DecimalEx" Version="1.0.2" />
-    <PackageReference Include="OptimizedPriorityQueue" Version="4.2.0" />
+    <PackageReference Include="OptimizedPriorityQueue" Version="5.1.0" />
     <PackageReference Include="Serilog" Version="2.10.0" />
     <PackageReference Include="SonarAnalyzer.CSharp" Version="8.38.0.46746">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>