diff --git a/src/NHibernate/NHibernate.csproj b/src/NHibernate/NHibernate.csproj
index 3fb89402ad..d370a6fae0 100644
--- a/src/NHibernate/NHibernate.csproj
+++ b/src/NHibernate/NHibernate.csproj
@@ -37,7 +37,7 @@
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-    <PackageReference Include="Iesi.Collections" Version="[4.0.4, 5.0)" />
+    <PackageReference Include="Iesi.Collections" Version="4.1.1" />
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.1.1" PrivateAssets="All" />
     <PackageReference Include="Remotion.Linq" Version="[2.2.0, 3.0)" />
     <PackageReference Include="Remotion.Linq.EagerFetching" Version="[2.2.0, 3.0)" />