diff --git a/agent/windows-setup-agent/SetupWizard.cs b/agent/windows-setup-agent/SetupWizard.cs
index 9150d0677..10aabdb0a 100644
--- a/agent/windows-setup-agent/SetupWizard.cs
+++ b/agent/windows-setup-agent/SetupWizard.cs
@@ -41,7 +41,7 @@ namespace Icinga
 				if (props.DomainName != "")
 					fqdn += "." + props.DomainName;
 
-				return fqdn;
+				return fqdn.ToLower();
 			}
 		}