diff --git a/lib/irb/input-method.rb b/lib/irb/input-method.rb
index b0110dd09b..5f13971a43 100644
--- a/lib/irb/input-method.rb
+++ b/lib/irb/input-method.rb
@@ -296,8 +296,13 @@ module IRB
         end
       Reline.dig_perfect_match_proc = IRB::InputCompletor::PerfectMatchedProc
       Reline.autocompletion = IRB.conf[:USE_AUTOCOMPLETE]
+
       if IRB.conf[:USE_AUTOCOMPLETE]
-        Reline.add_dialog_proc(:show_doc, SHOW_DOC_DIALOG, Reline::DEFAULT_DIALOG_CONTEXT)
+        begin
+          require 'rdoc'
+          Reline.add_dialog_proc(:show_doc, SHOW_DOC_DIALOG, Reline::DEFAULT_DIALOG_CONTEXT)
+        rescue LoadError
+        end
       end
     end
 
@@ -321,11 +326,6 @@ module IRB
         [195, 164], # The "ä" that appears when Alt+d is pressed on xterm.
         [226, 136, 130] # The "∂" that appears when Alt+d in pressed on iTerm2.
       ]
-      begin
-        require 'rdoc'
-      rescue LoadError
-        return nil
-      end
 
       if just_cursor_moving and completion_journey_data.nil?
         return nil