diff --git a/lib/irb/completion.rb b/lib/irb/completion.rb
index 723674738..9e3db1f87 100644
--- a/lib/irb/completion.rb
+++ b/lib/irb/completion.rb
@@ -144,7 +144,7 @@ def self.retrieve_completion_data(input, bind: IRB.conf[:MAIN_CONTEXT].workspace
           select_message(receiver, message, candidates, sep)
         end
 
-      when /^(?<num>-?(0[dbo])?[0-9_]+(\.[0-9_]+)?(([eE][+-]?[0-9]+)?i?|r)?)(?<sep>\.|::)(?<mes>[^.]*)$/
+      when /^(?<num>-?(?:0[dbo])?[0-9_]+(?:\.[0-9_]+)?(?:(?:[eE][+-]?[0-9]+)?i?|r)?)(?<sep>\.|::)(?<mes>[^.]*)$/
         # Numeric
         receiver = $~[:num]
         sep = $~[:sep]