diff --git a/lib/net/imap.rb b/lib/net/imap.rb
index c94e236a..3adb2d7f 100644
--- a/lib/net/imap.rb
+++ b/lib/net/imap.rb
@@ -2501,6 +2501,7 @@ def idle_done
     #
     #   Calling without a block is unsafe and deprecated.  Future releases will
     #   raise ArgumentError unless a block is given.
+    #   See Config#responses_without_block.
     #
     # Previously unhandled responses are automatically cleared before entering a
     # mailbox with #select or #examine.  Long-lived connections can receive many
@@ -2525,7 +2526,12 @@ def responses(type = nil)
       elsif type
         raise ArgumentError, "Pass a block or use #clear_responses"
       else
-        # warn("DEPRECATED: pass a block or use #clear_responses", uplevel: 1)
+        case config.responses_without_block
+        when :raise
+          raise ArgumentError, "Pass a block or use #clear_responses"
+        when :warn
+          warn("DEPRECATED: pass a block or use #clear_responses", uplevel: 1)
+        end
         @responses
       end
     end
diff --git a/lib/net/imap/config.rb b/lib/net/imap/config.rb
index 4194936a..f2909ac2 100644
--- a/lib/net/imap/config.rb
+++ b/lib/net/imap/config.rb
@@ -114,6 +114,21 @@ def self.[](config) # :nodoc: unfinished API
       # | v0.4                  | +true+  <em>(support added)</em>         |
       attr_accessor :sasl_ir, type: :boolean
 
+      # :markup: markdown
+      #
+      # Controls the behavior of Net::IMAP#responses when called without a
+      # block.  Valid options are `:warn`, `:raise`, or
+      # `:silence_deprecation_warning`.
+      #
+      # | Starting with version | The default value is           |
+      # |-----------------------|--------------------------------|
+      # | v0.4.13               | +:silence_deprecation_warning+ |
+      # | v0.5                  | +:warn+                        |
+      # | _eventually_          | +:raise+                       |
+      attr_accessor :responses_without_block, type: [
+        :silence_deprecation_warning, :warn, :raise,
+      ]
+
       # Creates a new config object and initialize its attribute with +attrs+.
       #
       # If +parent+ is not given, the global config is used by default.
@@ -130,6 +145,7 @@ def initialize(parent = Config.global, **attrs)
         open_timeout: 30,
         idle_response_timeout: 5,
         sasl_ir: true,
+        responses_without_block: :silence_deprecation_warning,
       ).freeze
 
       @global = default.new
diff --git a/lib/net/imap/config/attr_type_coercion.rb b/lib/net/imap/config/attr_type_coercion.rb
index 7511193d..51fd8ffd 100644
--- a/lib/net/imap/config/attr_type_coercion.rb
+++ b/lib/net/imap/config/attr_type_coercion.rb
@@ -26,6 +26,7 @@ def self.attr_accessor(attr, type: nil)
           return unless type
           if    :boolean == type then boolean attr
           elsif Integer  == type then integer attr
+          elsif Array   === type then enum    attr, type
           else raise ArgumentError, "unknown type coercion %p" % [type]
           end
         end
@@ -39,6 +40,17 @@ def self.integer(attr)
           define_method :"#{attr}=" do |val| super Integer val end
         end
 
+        def self.enum(attr, enum)
+          enum = enum.dup.freeze
+          expected = -"one of #{enum.map(&:inspect).join(", ")}"
+          define_method :"#{attr}=" do |val|
+            unless enum.include?(val)
+              raise ArgumentError, "expected %s, got %p" % [expected, val]
+            end
+            super val
+          end
+        end
+
       end
     end
   end
diff --git a/test/net/imap/test_config.rb b/test/net/imap/test_config.rb
index e14d7b74..1b97813f 100644
--- a/test/net/imap/test_config.rb
+++ b/test/net/imap/test_config.rb
@@ -50,6 +50,22 @@ class ConfigTest < Test::Unit::TestCase
     assert_equal 333, config.open_timeout
   end
 
+  test "enum type constraint" do
+    config = Config.new
+    config.responses_without_block = :silence_deprecation_warning
+    assert_equal :silence_deprecation_warning, config.responses_without_block
+    config.responses_without_block = :warn
+    assert_equal :warn, config.responses_without_block
+    config.responses_without_block = :raise
+    assert_equal :raise, config.responses_without_block
+    assert_raise(ArgumentError) do config.responses_without_block = false end
+    assert_equal :raise, config.responses_without_block
+    assert_raise(ArgumentError) do config.responses_without_block = 12345 end
+    assert_equal :raise, config.responses_without_block
+    assert_raise(ArgumentError) do config.responses_without_block = "warn" end
+    assert_equal :raise, config.responses_without_block
+  end
+
   test ".default" do
     default = Config.default
     assert default.equal?(Config.default)
diff --git a/test/net/imap/test_imap.rb b/test/net/imap/test_imap.rb
index ff8c3109..558e7e0f 100644
--- a/test/net/imap/test_imap.rb
+++ b/test/net/imap/test_imap.rb
@@ -1122,10 +1122,22 @@ def test_responses
       assert_equal(1, imap.responses("RECENT", &:last))
       assert_raise(ArgumentError) do imap.responses("UIDNEXT") end
       # Deprecated style, without a block:
-      # assert_warn(/Pass a block.*or.*clear_responses/i) do
-      #   assert_equal(%i[Answered Flagged Deleted Seen Draft],
-      #                imap.responses["FLAGS"]&.last)
-      # end
+      imap.config.responses_without_block = :raise
+      assert_raise(ArgumentError) do imap.responses end
+      imap.config.responses_without_block = :warn
+      assert_raise(ArgumentError) do imap.responses("UIDNEXT") end
+      assert_warn(/Pass a block.*or.*clear_responses/i) do
+        assert_equal(%i[Answered Flagged Deleted Seen Draft],
+                     imap.responses["FLAGS"]&.last)
+      end
+      # TODO: assert_no_warn?
+      imap.config.responses_without_block = :silence_deprecation_warning
+      assert_raise(ArgumentError) do imap.responses("UIDNEXT") end
+      stderr = EnvUtil.verbose_warning {
+        assert_equal(%i[Answered Flagged Deleted Seen Draft],
+                     imap.responses["FLAGS"]&.last)
+      }
+      assert_empty stderr
     end
   end