diff --git a/lib/kamal/configuration.rb b/lib/kamal/configuration.rb
index 04c870a8..c171631b 100644
--- a/lib/kamal/configuration.rb
+++ b/lib/kamal/configuration.rb
@@ -288,7 +288,7 @@ class Kamal::Configuration
     end
 
     def ensure_valid_service_name
-      raise ArgumentError, "Service name can only include alphanumeric characters, hyphens, and underscores" unless raw_config[:service] =~ /^[a-z0-9-_]+$/
+      raise ArgumentError, "Service name can only include alphanumeric characters, hyphens, and underscores" unless raw_config[:service] =~ /^[a-z0-9_-]+$/
 
       true
     end