diff --git a/lib/iruby/application.rb b/lib/iruby/application.rb
index 6760322..47187b7 100644
--- a/lib/iruby/application.rb
+++ b/lib/iruby/application.rb
@@ -104,7 +104,7 @@ def run
       when :unregister
         unregister_kernel(@sub_argv)
       when :console
-        exec_jupyter(@sub_cmd.to_s, @sub_argv)
+        exec_jupyter(@sub_argv)
       when :kernel
         @sub_app = KernelApplication.new(@sub_argv)
         @sub_app.run
@@ -336,7 +336,7 @@ def unregister_kernel(argv)
       params
     end
 
-    def exec_jupyter(sub_cmd, argv)
+    def exec_jupyter(argv)
       opts = OptionParser.new
       opts.banner = "Usage: #{$PROGRAM_NAME} unregister [options]"
 
diff --git a/lib/iruby/kernel.rb b/lib/iruby/kernel.rb
index ab3fe4a..9686688 100644
--- a/lib/iruby/kernel.rb
+++ b/lib/iruby/kernel.rb
@@ -92,9 +92,9 @@ def initialize(config_file, session_adapter_name=nil)
     def switch_backend!(backend)
       name = case backend
              when String, Symbol
-               name = backend.downcase
+               backend.downcase
              else
-               name = backend
+               backend
              end
 
       backend_class = case name