diff --git a/lib/debug/completor.rb b/lib/debug/completor.rb
new file mode 100644
index 000000000..b6a485a0e
--- /dev/null
+++ b/lib/debug/completor.rb
@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+require "irb/completion"
+
+module DEBUGGER__
+  class Completor
+    class << self
+      # old IRB completion API
+      if defined?(IRB::InputCompletor)
+        def retrieve_completion_data(input, binding)
+          IRB::InputCompletor.retrieve_completion_data(input, bind: binding).compact
+        end
+      else
+        COMPLETOR = IRB::RegexpCompletor.new
+
+        def retrieve_completion_data(input, binding)
+          COMPLETOR.retrieve_completion_data(input, bind: binding, doc_namespace: false).compact
+        end
+      end
+    end
+  end
+end
diff --git a/lib/debug/server_dap.rb b/lib/debug/server_dap.rb
index 8dbefda8a..6328a462e 100644
--- a/lib/debug/server_dap.rb
+++ b/lib/debug/server_dap.rb
@@ -5,6 +5,8 @@
 require 'tmpdir'
 require 'fileutils'
 
+require_relative 'completor'
+
 module DEBUGGER__
   module UI_DAP
     SHOW_PROTOCOL = ENV['DEBUG_DAP_SHOW_PROTOCOL'] == '1' || ENV['RUBY_DEBUG_DAP_SHOW_PROTOCOL'] == '1'
@@ -980,7 +982,7 @@ def process_dap args
         frame = get_frame(fid)
 
         if (b = frame&.binding) && word = text&.split(/[\s\{]/)&.last
-          words = IRB::InputCompletor::retrieve_completion_data(word, bind: b).compact
+          words = Completor.retrieve_completion_data(word, b)
         end
 
         event! :protocol_result, :completions, req, targets: (words || []).map{|phrase|