diff --git a/lib/guard.rb b/lib/guard.rb
index 4a985aa..7cd574f 100644
--- a/lib/guard.rb
+++ b/lib/guard.rb
@@ -241,13 +241,13 @@ module Guard
     def debug_command_execution
       Kernel.send(:alias_method, :original_system, :system)
       Kernel.send(:define_method, :system) do |command, *args|
-        ::Guard::UI.debug 'Command execution: #{command} #{args.join(' ')}'
+        ::Guard::UI.debug "Command execution: #{ command } #{ args.join(' ') }"
         original_system command, *args
       end
 
       Kernel.send(:alias_method, :original_backtick, :'`')
       Kernel.send(:define_method, :'`') do |command|
-        ::Guard::UI.debug 'Command execution: #{command}'
+        ::Guard::UI.debug "Command execution: #{ command }"
         original_backtick command
       end
     end