diff --git a/src/Serilog.Sinks.Elasticsearch/Sinks/ElasticSearch/ElasticSearchSink.cs b/src/Serilog.Sinks.Elasticsearch/Sinks/ElasticSearch/ElasticSearchSink.cs
index fec5d5ff..a49bfe9f 100644
--- a/src/Serilog.Sinks.Elasticsearch/Sinks/ElasticSearch/ElasticSearchSink.cs
+++ b/src/Serilog.Sinks.Elasticsearch/Sinks/ElasticSearch/ElasticSearchSink.cs
@@ -156,7 +156,7 @@ protected virtual void HandleException(Exception ex, IEnumerable<LogEvent> event
         // Helper function: checks if a given dynamic member / dictionary key exists at runtime
         private static bool HasProperty(dynamic settings, string name)
         {
-            if (settings is System.Dynamic.ExpandoObject)
+            if (settings is IDictionary<string, object>)
                 return ((IDictionary<string, object>)settings).ContainsKey(name);
 
             if (settings is System.Dynamic.DynamicObject)