diff --git a/lib/irb/init.rb b/lib/irb/init.rb
index d474bd41d..ee07862cd 100644
--- a/lib/irb/init.rb
+++ b/lib/irb/init.rb
@@ -79,7 +79,7 @@ def IRB.init_config(ap_path)
 
     @CONF[:USE_SINGLELINE] = false unless defined?(ReadlineInputMethod)
     @CONF[:USE_COLORIZE] = (nc = ENV['NO_COLOR']).nil? || nc.empty?
-    @CONF[:USE_AUTOCOMPLETE] = ENV.fetch("IRB_USE_AUTOCOMPLETE", "true") != "false"
+    @CONF[:USE_AUTOCOMPLETE] = ENV.fetch("IRB_USE_AUTOCOMPLETE", "false") != "false"
     @CONF[:COMPLETOR] = ENV["IRB_COMPLETOR"]&.to_sym
     @CONF[:INSPECT_MODE] = true
     @CONF[:USE_TRACER] = false
diff --git a/test/irb/test_context.rb b/test/irb/test_context.rb
index 9fa23ccce..71f256d8b 100644
--- a/test/irb/test_context.rb
+++ b/test/irb/test_context.rb
@@ -215,7 +215,7 @@ def inspect
     end
 
     def test_default_config
-      assert_equal(true, @context.use_autocomplete?)
+      assert_equal(false, @context.use_autocomplete?)
     end
 
     def test_echo_on_assignment
diff --git a/test/irb/test_init.rb b/test/irb/test_init.rb
index f7168e02f..99b79b60b 100644
--- a/test/irb/test_init.rb
+++ b/test/irb/test_init.rb
@@ -145,7 +145,7 @@ def test_use_autocomplete_environment_variable
 
       ENV['IRB_USE_AUTOCOMPLETE'] = nil
       IRB.setup(__FILE__)
-      assert IRB.conf[:USE_AUTOCOMPLETE]
+      refute IRB.conf[:USE_AUTOCOMPLETE]
 
       ENV['IRB_USE_AUTOCOMPLETE'] = ''
       IRB.setup(__FILE__)
diff --git a/test/irb/test_type_completor.rb b/test/irb/test_type_completor.rb
index 3d0e25d19..2697eed88 100644
--- a/test/irb/test_type_completor.rb
+++ b/test/irb/test_type_completor.rb
@@ -101,7 +101,6 @@ def test_type_completor
         type "puts completor.doc_namespace 'a = n.chr;', 'a.encoding', '', bind: binding"
         type "exit!"
       end
-      assert_match(/Completion: Autocomplete, ReplTypeCompletor/, output)
       assert_match(/a\.bit_length/, output)
       assert_match(/String#encoding/, output)
     end