diff --git a/lib/engineyard/model/instance.rb b/lib/engineyard/model/instance.rb
index d8a167e..3a7807e 100644
--- a/lib/engineyard/model/instance.rb
+++ b/lib/engineyard/model/instance.rb
@@ -120,10 +120,10 @@ def invoke_engineyard_serverside(deploy_args, verbose=false)
           instance_args << '--instances'
           instance_args += instances.collect { |i| i.public_hostname }
 
-          instance_args << '--instance_roles'
+          instance_args << '--instance-roles'
           instance_args += instances.collect { |i| [i.public_hostname, i.role].join(':') }
 
-          instance_args << '--instance_names'
+          instance_args << '--instance-names'
           instance_args += instances.collect { |i| i.name ? [i.public_hostname, i.name].join(':') : nil }.compact
         end
 
diff --git a/spec/support/shared_behavior.rb b/spec/support/shared_behavior.rb
index b7e8e7c..f57625e 100644
--- a/spec/support/shared_behavior.rb
+++ b/spec/support/shared_behavior.rb
@@ -151,8 +151,8 @@ def make_scenario(hash)
     it "passes along instance information to engineyard-serverside" do
       instance_args = [
         /--instances app_master[^\s]+ app_hostname[^\s]+ util_fluffy/,
-        /--instance_roles app_master[^\s]+:app_master app_hostname[^\s]+:app util_fluffy[^\s]+:util/,
-        /--instance_names util_fluffy[^\s]+:fluffy/
+        /--instance-roles app_master[^\s]+:app_master app_hostname[^\s]+:app util_fluffy[^\s]+:util/,
+        /--instance-names util_fluffy[^\s]+:fluffy/
       ]
 
       db_instance = /db_master/