diff --git a/src/GenericQueryable/Fetching/FetchRuleHeaderExpander.cs b/src/GenericQueryable/Fetching/FetchRuleHeaderExpander.cs
index 07efc28..0f34818 100644
--- a/src/GenericQueryable/Fetching/FetchRuleHeaderExpander.cs
+++ b/src/GenericQueryable/Fetching/FetchRuleHeaderExpander.cs
@@ -14,9 +14,14 @@ public class FetchRuleHeaderExpander(IEnumerable<FetchRuleHeaderInfo> fetchRuleH
     public FetchRule<TSource>? TryExpand<TSource>(FetchRule<TSource> fetchRule)
     {
         return cache.GetOrAdd(typeof(TSource),
-                _ => headersDict[typeof(TSource)].Cast<FetchRuleHeaderInfo<TSource>>()
+                _ => headersDict
+                    .GetValueOrDefault(typeof(TSource))
+                    .EmptyIfNull()
+                    .Cast<FetchRuleHeaderInfo<TSource>>()
                     .ToDictionary(info => info.Header, info => info.Implementation))
+
             .Pipe(innerCache => (IReadOnlyDictionary<FetchRule<TSource>, FetchRule<TSource>>)innerCache)
+
             .Pipe(innerCache => innerCache.GetValueOrDefault(fetchRule));
     }
 }
\ No newline at end of file
diff --git a/src/__SolutionItems/CommonAssemblyInfo.cs b/src/__SolutionItems/CommonAssemblyInfo.cs
index baee29e..436881a 100644
--- a/src/__SolutionItems/CommonAssemblyInfo.cs
+++ b/src/__SolutionItems/CommonAssemblyInfo.cs
@@ -3,7 +3,7 @@
 [assembly: AssemblyProduct("GenericQueryable")]
 [assembly: AssemblyCompany("IvAt")]
 
-[assembly: AssemblyVersion("2.0.4.0")]
+[assembly: AssemblyVersion("2.0.5.0")]
 [assembly: AssemblyInformationalVersion("changes at build")]
 
 #if DEBUG