diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index e1c168217..78790c6dc 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -29,6 +29,7 @@ jobs:
         ruby-version: ${{ matrix.ruby }}
     - name: Install dependencies
       run: |
+        gem update --system
         gem install bundler --no-document
         bundle install
     - name: Run test
diff --git a/irb.gemspec b/irb.gemspec
index e75592270..881839532 100644
--- a/irb.gemspec
+++ b/irb.gemspec
@@ -36,5 +36,5 @@ Gem::Specification.new do |spec|
 
   spec.required_ruby_version = Gem::Requirement.new(">= 2.5")
 
-  spec.add_dependency "reline", ">= 0.2.7"
+  spec.add_dependency "reline", ">= 0.2.8.pre.1"
 end
diff --git a/lib/irb/input-method.rb b/lib/irb/input-method.rb
index 1854567a2..4d55e4ef3 100644
--- a/lib/irb/input-method.rb
+++ b/lib/irb/input-method.rb
@@ -14,6 +14,7 @@
 require_relative 'completion'
 require 'io/console'
 require 'reline'
+require 'rdoc'
 
 module IRB
   STDIN_FILE_NAME = "(line)" # :nodoc:
@@ -308,6 +309,50 @@ def auto_indent(&block)
       @auto_indent_proc = block
     end
 
+    SHOW_DOC_DIALOG = ->() {
+      begin
+        require 'rdoc'
+      rescue LoadError
+        return nil
+      end
+      if just_cursor_moving and completion_journey_data.nil?
+        return nil
+      end
+      cursor_pos_to_render, result, pointer = context.pop(3)
+      return nil if result.nil? or pointer.nil?
+      name = result[pointer]
+
+      driver = RDoc::RI::Driver.new
+      begin
+        name = driver.expand_name(name)
+      rescue RDoc::RI::Driver::NotFoundError
+        return nil
+      end
+      doc = nil
+      used_for_class = false
+      if not name =~ /#|\./
+        found, klasses, includes, extends = driver.classes_and_includes_and_extends_for(name)
+        if not found.empty?
+          doc = driver.class_document(name, found, klasses, includes, extends)
+          used_for_class = true
+        end
+      end
+      unless used_for_class
+        doc = RDoc::Markup::Document.new
+        begin
+          driver.add_method(doc, name)
+        rescue RDoc::RI::Driver::NotFoundError
+          doc = nil
+        end
+      end
+      return nil if doc.nil?
+      formatter = RDoc::Markup::ToAnsi.new
+      formatter.width = 40
+      str = doc.accept(formatter)
+
+      [Reline::CursorPos.new(cursor_pos_to_render.x + 40, cursor_pos_to_render.y + pointer), str.split("\n"), nil, '49']
+    }
+
     # Reads the next line from this input method.
     #
     # See IO#gets for more information.
@@ -316,6 +361,7 @@ def gets
       Reline.output = @stdout
       Reline.prompt_proc = @prompt_proc
       Reline.auto_indent_proc = @auto_indent_proc if @auto_indent_proc
+      Reline.add_dialog_proc(:show_doc, SHOW_DOC_DIALOG, Reline::DEFAULT_DIALOG_CONTEXT)
       if l = readmultiline(@prompt, false, &@check_termination_proc)
         HISTORY.push(l) if !l.empty?
         @line[@line_no += 1] = l + "\n"