diff --git a/src/Serilog.Sinks.Splunk/Sinks/Splunk/SplunkJsonFormatter.cs b/src/Serilog.Sinks.Splunk/Sinks/Splunk/SplunkJsonFormatter.cs
index b2f2e6f..1f3d66d 100644
--- a/src/Serilog.Sinks.Splunk/Sinks/Splunk/SplunkJsonFormatter.cs
+++ b/src/Serilog.Sinks.Splunk/Sinks/Splunk/SplunkJsonFormatter.cs
@@ -76,7 +76,7 @@ public SplunkJsonFormatter(
 
             if (!string.IsNullOrWhiteSpace(sourceType))
             {
-                suffixWriter.Write(",\"sourceType\":");
+                suffixWriter.Write(",\"sourcetype\":");
                 JsonValueFormatter.WriteQuotedJsonString(sourceType, suffixWriter);
             }