diff --git a/src/storage/zone.cr b/src/storage/zone.cr
index 4f644e1..3cd1e3f 100644
--- a/src/storage/zone.cr
+++ b/src/storage/zone.cr
@@ -7,7 +7,7 @@ def label_pattern
 end
 
 def subdomain_pattern
-	/\b(?:[0-9A-Za-z][0-9A-Za-z-]{0,62})(?:\.(?:[0-9A-Za-z][0-9A-Za-z-]{0,62}))*\b/
+	/\b(?:[_0-9A-Za-z][0-9A-Za-z-]{0,62})(?:\.(?:[0-9A-Za-z][0-9A-Za-z-]{0,62}))*\b/
 end
 
 # /^(((?!-))(xn--|_{1,1})?[a-z0-9-]{0,61}[a-z0-9]{1,1}\.)*