diff --git a/lib/dew/commands/deploy.rb b/lib/dew/commands/deploy.rb
index <HASH>..<HASH> 100755
--- a/lib/dew/commands/deploy.rb
+++ b/lib/dew/commands/deploy.rb
@@ -45,6 +45,7 @@ class DeployCommand < Clamp::Command
       end
 
       env = Environment.get(environment_name)
+      raise "Unknown environment #{environment_name}" unless env
 
       db_managed = false
Bail with error if environment unrecognized when deploying