diff --git a/lib/net/imap.rb b/lib/net/imap.rb
index bf24ba03..06d7bf25 100644
--- a/lib/net/imap.rb
+++ b/lib/net/imap.rb
@@ -2528,11 +2528,11 @@ def idle_done
     #       Prints a warning and returns the mutable responses hash.
     #       <em>This is not thread-safe.</em>
     #
-    #     [+:frozen_dup+</em>]
+    #     [+:frozen_dup+ <em>(planned default for +v0.6+)</em>]
     #       Returns a frozen copy of the unhandled responses hash, with frozen
     #       array values.
     #
-    #     [+:raise+ <em>(planned future default)</em>]
+    #     [+:raise+]
     #       Raise an +ArgumentError+ with the deprecation warning.
     #
     # For example:
diff --git a/lib/net/imap/config.rb b/lib/net/imap/config.rb
index 1ebced23..7532737c 100644
--- a/lib/net/imap/config.rb
+++ b/lib/net/imap/config.rb
@@ -260,7 +260,7 @@ def self.[](config)
       #   Prints a warning and returns the mutable responses hash.
       #   <em>This is not thread-safe.</em>
       #
-      # [+:frozen_dup+</em>]
+      # [+:frozen_dup+ <em>(planned default for +v0.6+)</em>]
       #   Returns a frozen copy of the unhandled responses hash, with frozen
       #   array values.
       #
@@ -269,7 +269,7 @@ def self.[](config)
       #
       #   <em>(+:frozen_dup+ config option was added in +v0.4.17+)</em>
       #
-      # [+:raise+ <em>(planned future default)</em>]
+      # [+:raise+]
       #   Raise an ArgumentError with the deprecation warning.
       #
       # Note: #responses_without_args is an alias for #responses_without_block.
@@ -388,12 +388,11 @@ def defaults_hash
 
       version_defaults[0.5] = Config[:current]
 
-      version_defaults[0.6] = Config[0.5]
-      version_defaults[:next] = Config[0.6]
-
-      version_defaults[:future]  = Config[0.6].dup.update(
-        responses_without_block: :raise,
+      version_defaults[0.6] = Config[0.5].dup.update(
+        responses_without_block: :frozen_dup,
       ).freeze
+      version_defaults[:next] = Config[0.6]
+      version_defaults[:future] = Config[:next]
 
       version_defaults.freeze
     end
diff --git a/test/net/imap/test_config.rb b/test/net/imap/test_config.rb
index 6c709735..fa11c74a 100644
--- a/test/net/imap/test_config.rb
+++ b/test/net/imap/test_config.rb
@@ -190,7 +190,7 @@ class ConfigTest < Test::Unit::TestCase
     assert_same Config.default, Config.new(Config.default).parent
     assert_same Config.global,  Config.new(Config.global).parent
     assert_same Config[0.4],    Config.new(0.4).parent
-    assert_same Config[0.5],    Config.new(:next).parent
+    assert_same Config[0.6],    Config.new(:next).parent
     assert_equal true, Config.new({debug: true}, debug: false).parent.debug?
     assert_equal true, Config.new({debug: true}, debug: false).parent.frozen?
   end