diff --git a/lib/fog/compute/models/aws/server.rb b/lib/fog/compute/models/aws/server.rb
index 39d3d8f9e..4d90df98b 100644
--- a/lib/fog/compute/models/aws/server.rb
+++ b/lib/fog/compute/models/aws/server.rb
@@ -177,8 +177,11 @@ module Fog
         end
 
         def ssh(commands)
-          requires :identity, :ip_address, :private_key, :username
-          Fog::SSH.new(ip_address, username, :key_data => [private_key]).run(commands)
+          requires :identity, :ip_address, :username
+
+          options = {}
+          options[:key_data] = [private_key] if private_key
+          Fog::SSH.new(ip_address, username, options).run(commands)
         end
 
         def start
diff --git a/lib/fog/compute/models/bluebox/server.rb b/lib/fog/compute/models/bluebox/server.rb
index 126926f50..d241f0e64 100644
--- a/lib/fog/compute/models/bluebox/server.rb
+++ b/lib/fog/compute/models/bluebox/server.rb
@@ -108,8 +108,11 @@ module Fog
         end
 
         def ssh(commands)
-          requires :identity, :ips, :private_key, :username
-          Fog::SSH.new(ips.first['address'], username, :key_data => [private_key]).run(commands)
+          requires :identity, :ips, :username
+
+          options = {}
+          options[:key_data] = [private_key] if private_key
+          Fog::SSH.new(ips.first['address'], username, options).run(commands)
         end
 
         def username
diff --git a/lib/fog/compute/models/rackspace/server.rb b/lib/fog/compute/models/rackspace/server.rb
index 87f7959e1..1dacf4618 100644
--- a/lib/fog/compute/models/rackspace/server.rb
+++ b/lib/fog/compute/models/rackspace/server.rb
@@ -104,8 +104,11 @@ module Fog
         end
 
         def ssh(commands)
-          requires :addresses, :identity, :private_key, :username
-          Fog::SSH.new(addresses['public'].first, username, :key_data => [private_key]).run(commands)
+          requires :addresses, :identity, :username
+
+          options = {}
+          options[:key_data] = [private_key] if private_key
+          Fog::SSH.new(addresses['public'].first, username, options).run(commands)
         end
 
         def username
diff --git a/lib/fog/compute/models/slicehost/server.rb b/lib/fog/compute/models/slicehost/server.rb
index b37c77555..07b4a4a79 100644
--- a/lib/fog/compute/models/slicehost/server.rb
+++ b/lib/fog/compute/models/slicehost/server.rb
@@ -94,8 +94,11 @@ module Fog
         end
 
         def ssh(commands)
-          requires :addresses, :identity, :private_key, :username
-          Fog::SSH.new(addresses.first, username, :key_data => [private_key]).run(commands)
+          requires :addresses, :identity, :username
+
+          options = {}
+          options[:key_data] = [private_key] if private_key
+          Fog::SSH.new(addresses.first, username, options).run(commands)
         end
 
         def username