diff --git a/src/Umbraco.PublishedCache.NuCache/Property.cs b/src/Umbraco.PublishedCache.NuCache/Property.cs
index 09716ef43a35..41532d4944c1 100644
--- a/src/Umbraco.PublishedCache.NuCache/Property.cs
+++ b/src/Umbraco.PublishedCache.NuCache/Property.cs
@@ -240,7 +240,7 @@ private CacheValues GetCacheValues(IAppCache? cache)
 
         EnsureSourceValuesInitialized();
 
-        var k = new CompositeStringStringKey(culture, segment);
+        var k = new CompositeStringStringKey(culture ?? string.Empty, segment ?? string.Empty); // Null values are not valid when creating a CompositeStringStringKey.
 
         SourceInterValue vvalue = _sourceValues!.GetOrAdd(k, _ =>
             new SourceInterValue