1 files changed, 4 insertions, 0 deletions
diff --git a/lib/irb/init.rb b/lib/irb/init.rb
index 344b243f12..2066d8cb64 100644
--- a/lib/irb/init.rb
+++ b/lib/irb/init.rb
@@ -112,6 +112,8 @@ module IRB # :nodoc:
     @CONF[:LC_MESSAGES] = Locale.new
 
     @CONF[:AT_EXIT] = []
+
+    @CONF[:DEBUG_LEVEL] = 0
   end
 
   def IRB.init_error
@@ -189,6 +191,8 @@ module IRB # :nodoc:
         @CONF[:CONTEXT_MODE] = ($1 || argv.shift).to_i
       when "--single-irb"
         @CONF[:SINGLE_IRB] = true
+      when /^--irb_debug(?:=(.+))?/
+        @CONF[:DEBUG_LEVEL] = ($1 || argv.shift).to_i
       when "-v", "--version"
         print IRB.version, "\n"
         exit 0