diff --git a/CHANGELOG.md b/CHANGELOG.md
index aff3fe5..1e2423b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,7 @@
 ## [Unreleased]
 
 - Drop `:process` and `:thread` workers since there are no concrete use cases.
+- Drop `:experimental_ractor_rspec_integration` option since there are no concrete use cases.
 
 ## [0.4.2] - 2024-05-23
 
diff --git a/Gemfile b/Gemfile
index caae970..a4abdbe 100644
--- a/Gemfile
+++ b/Gemfile
@@ -7,5 +7,4 @@ gemspec
 gem "rake"
 gem "rspec"
 gem "standard"
-gem "prism"
 gem "benchmark-ips"
diff --git a/README.md b/README.md
index fff5882..169e0ed 100644
--- a/README.md
+++ b/README.md
@@ -231,9 +231,6 @@ Pbt.configure do |config|
   # Whether to report exceptions in threads.
   # It's useful to suppress error logs on Ractor that reports many errors. Default is `false`.
   config.thread_report_on_exception = false
-
-  # Whether to allow RSpec expectation and matchers in Ractor. It's quite experimental! Default is `false`.
-  config.experimental_ractor_rspec_integration = false
 end
 ```
 
@@ -295,22 +292,6 @@ it do
 end
 ```
 
-If you're a challenger, you can enable the experimental feature to allow using RSpec expectations and matchers in Ractor. It works but it's quite experimental and could cause unexpected behaviors.
-
-Please note that this feature depends on [prism](https://ruby.github.io/prism/) gem. If you use Ruby 3.2 or prior, you need to install the gem by yourself.
-
-```ruby
-it do
-  Pbt.assert(worker: :ractor, experimental_ractor_rspec_integration: true) do
-    Pbt.property(Pbt.integer) do |n|
-      # Some RSpec expectations and matchers are available in Ractor by hack.
-      # Other features like `let`, `subject`, `before`, `after` that access out of block are still not available.
-      expect(n).to be_an(Integer)
-    end
-  end
-end
-```
-
 ### None
 
 For most cases, `:none` is the best choice. It runs tests sequentially but most test cases finishes within a reasonable time.
@@ -341,7 +322,7 @@ Once this project finishes the following, we will release v1.0.0.
   - [x] Configuration
 - [x] Benchmark
 - [x] Rich report by verbose mode
-- [x] (Partially) Allow to use expectations and matchers provided by test framework in Ractor if possible.
+- [x] (Partially) Allow to use expectations and matchers provided by test framework in Ractor. (dropped)
   - It'd be so hard to pass assertions like `expect`, `assert` to a Ractor.
 - [ ] Implement frequency arbitrary
 - [ ] Statistics feature to aggregate generated values
diff --git a/lib/pbt/check/configuration.rb b/lib/pbt/check/configuration.rb
index 3105f94..2446a5b 100644
--- a/lib/pbt/check/configuration.rb
+++ b/lib/pbt/check/configuration.rb
@@ -9,7 +9,6 @@ module Check
       :num_runs,
       :seed,
       :thread_report_on_exception,
-      :experimental_ractor_rspec_integration,
       keyword_init: true
     ) do
       # @param verbose [Boolean] Whether to print verbose output. Default is `false`.
@@ -17,14 +16,12 @@ module Check
       # @param num_runs [Integer] The number of runs to perform. Default is `100`.
       # @param seed [Integer] The seed to use for random number generation. It's useful to reproduce failed test with the seed you'd pick up from failure messages. Default is a random seed.
       # @param thread_report_on_exception [Boolean] Whether to report exceptions in threads. It's useful to suppress error logs on Ractor that reports many errors. Default is `false`.
-      # @param experimental_ractor_rspec_integration [Boolean] Whether to allow RSpec expectation and matchers in Ractor. It's quite experimental! Default is `false`.
       def initialize(
         verbose: false,
         worker: :none,
         num_runs: 100,
         seed: Random.new_seed,
-        thread_report_on_exception: false,
-        experimental_ractor_rspec_integration: false
+        thread_report_on_exception: false
       )
         super
       end
diff --git a/lib/pbt/check/rspec_adapter/integration.rb b/lib/pbt/check/rspec_adapter/integration.rb
deleted file mode 100644
index 32492f8..0000000
--- a/lib/pbt/check/rspec_adapter/integration.rb
+++ /dev/null
@@ -1,64 +0,0 @@
-# frozen_string_literal: true
-
-unless defined?(RSpec)
-  raise InvalidConfigurationError, "You configured `experimental_ractor_rspec_integration: true` but RSpec is not loaded. Please use RSpec or set the config `false`."
-end
-
-require "pbt/check/rspec_adapter/predicate_block_inspector"
-require "pbt/check/rspec_adapter/property_extension"
-
-module Pbt
-  module Check
-    # @private
-    module RSpecAdapter
-      # This custom error contains RSpec matcher and message to handle Pbt's runner.
-      # @private
-      class ExpectationNotMet < StandardError
-        attr_reader :matcher, :custom_message, :failure_message_method
-
-        def initialize(msg, matcher, custom_message, failure_message_method)
-          super(msg)
-          @matcher = matcher
-          @custom_message = custom_message
-          @failure_message_method = failure_message_method
-        end
-      end
-    end
-  end
-end
-
-# `autoload` is not allowed in Ractor but RSpec uses autoload for matchers.
-# We need to load them in advance in order to be able to use them in Ractor.
-#
-# e.g. Ractor raises... `be_a_kind_of': require by autoload on non-main Ractor is not supported (BeAKindOf) (Ractor::UnsafeError)
-RSpec::Matchers::BuiltIn.constants.each { |c| Object.const_get("RSpec::Matchers::BuiltIn::#{c}") }
-
-# TODO: preload more helpers like aggregate_failures.
-# RSpec::Expectations.constants.each { |c| Object.const_get("RSpec::Expectations::#{c}") }
-# The code above is not enough. Even if we run this code in advance, Ractor raises...
-# in `failure_notifier': can not access non-shareable objects in constant RSpec::Support::DEFAULT_FAILURE_NOTIFIER by non-main ractor. (Ractor::IsolationError)
-
-# CAUTION: This is a dirty hack! We need to override the original method to make it Ractor-safe.
-RSpec::Expectations::ExpectationHelper.singleton_class.prepend(Module.new do
-  def with_matcher(handler, matcher, message)
-    check_message(message)
-    matcher = modern_matcher_from(matcher)
-    yield matcher
-  ensure
-    # The original method is not Ractor-safe unless stopping assigning these class variables.
-    if Ractor.current == Ractor.main
-      ::RSpec::Matchers.last_expectation_handler = handler
-      ::RSpec::Matchers.last_matcher = matcher
-    end
-  end
-
-  def handle_failure(matcher, message, failure_message_method)
-    # This method is not Ractor-safe. RSpec::Support::ObjectFormatter.default_instance assigns class variables.
-    # If this method is called in non-main-Ractor, it raises a custom error and let it handle in the main Ractor.
-    if Ractor.current != Ractor.main
-      raise Pbt::Check::RSpecAdapter::ExpectationNotMet.new(nil, matcher, message, failure_message_method)
-    end
-
-    super
-  end
-end)
diff --git a/lib/pbt/check/rspec_adapter/predicate_block_inspector.rb b/lib/pbt/check/rspec_adapter/predicate_block_inspector.rb
deleted file mode 100644
index 6d211e5..0000000
--- a/lib/pbt/check/rspec_adapter/predicate_block_inspector.rb
+++ /dev/null
@@ -1,47 +0,0 @@
-# frozen_string_literal: true
-
-begin
-  # Use prism to get user-defined block code.
-  require "prism"
-rescue LoadError
-  raise InvalidConfiguration,
-    "Prism gem (https://github.com/ruby/prism) is required to use worker `:ractor` and `:experimental_ractor_rspec_integration`. Please add `gem 'prism'` to your Gemfile."
-end
-
-module Pbt
-  module Check
-    module RSpecAdapter
-      # This class is used to get user-defined block code.
-      # If a user defines code like below:
-      #
-      #   Pbt.property(Pbt.integer, Pbt.integer) do |x, y|
-      #     x > 0 && y > 0
-      #   end
-      #
-      #   inspector.method_params #=> "x, y"
-      #   inspector.method_body   #=> "x > 0 && y > 0"
-      #
-      # @private
-      # @!attribute [r] method_body
-      # @!attribute [r] method_params
-      class PredicateBlockInspector < Prism::Visitor
-        attr_reader :method_body, :method_params
-
-        def initialize(line)
-          @line = line
-          @method_body = nil
-          super()
-        end
-
-        def visit_call_node(node)
-          if node.name == :property && node.block.opening_loc.start_line == @line
-            @method_params = node.block.parameters.parameters.slice
-            @method_body = node.block.body.slice
-          end
-
-          super
-        end
-      end
-    end
-  end
-end
diff --git a/lib/pbt/check/rspec_adapter/property_extension.rb b/lib/pbt/check/rspec_adapter/property_extension.rb
deleted file mode 100644
index 1141f06..0000000
--- a/lib/pbt/check/rspec_adapter/property_extension.rb
+++ /dev/null
@@ -1,74 +0,0 @@
-# frozen_string_literal: true
-
-module Pbt
-  module Check
-    module RSpecAdapter
-      # @private
-      module PropertyExtension
-        # Define an original class to be called in Ractor.
-        #
-        # @return [void]
-        def setup_rspec_integration
-          filepath, line = @predicate.source_location
-          basename = File.basename(filepath, ".rb")
-          @class_name = "Test" + basename.split("_").map(&:capitalize).join + line.to_s
-          @method_name = "predicate_#{basename}_#{line}"
-          define_ractor_callable_class
-        end
-
-        # Clean up an original class to be called in Ractor to avoid any persisted namespace pollution.
-        #
-        # @return [void]
-        def teardown_rspec_integration
-          RSpecAdapter.__send__(:remove_const, @class_name) if RSpecAdapter.const_defined?(@class_name)
-        end
-
-        # Run the predicate with the generated `val`.
-        # This overrides the original `Property#run_in_ractor`.
-        #
-        # @param val [Object]
-        # @return [Ractor]
-        def run_in_ractor(val)
-          Ractor.new(@class_name, @method_name, @predicate.parameters.size, val) do |class_name, method_name, param_size, val|
-            klass = RSpecAdapter.const_get(class_name)
-            if val.is_a?(Hash)
-              klass.new.send(method_name, **val)
-            elsif param_size >= 2
-              klass.new.send(method_name, *val)
-            else
-              klass.new.send(method_name, val)
-            end
-          end
-        end
-
-        private
-
-        # @return [void]
-        def define_ractor_callable_class
-          # The @method_name is invisible in the Class.new block, so we need to assign it to a local variable.
-          method_name = @method_name
-
-          inspector = extract_predicate_source_code
-
-          RSpecAdapter.const_set(@class_name, Class.new do
-            include ::RSpec::Matchers
-            class_eval <<-RUBY, __FILE__, __LINE__ + 1
-            def #{method_name}(#{inspector.method_params})
-              #{inspector.method_body}
-            end
-            RUBY
-          end)
-        end
-
-        # @return [PredicateBlockInspector]
-        def extract_predicate_source_code
-          filepath, line = @predicate.source_location
-          PredicateBlockInspector.new(line).tap do |inspector|
-            res = Prism.parse_file(filepath)
-            res.value.statements.accept(inspector)
-          end
-        end
-      end
-    end
-  end
-end
diff --git a/lib/pbt/check/runner_methods.rb b/lib/pbt/check/runner_methods.rb
index 769720e..da43a27 100644
--- a/lib/pbt/check/runner_methods.rb
+++ b/lib/pbt/check/runner_methods.rb
@@ -54,8 +54,6 @@ def check(**options, &property)
       #
       # - `:thread_report_on_exception`
       #   So many exception reports happen in Ractor and a console gets too messy. Suppress them to avoid that.
-      # - `:experimental_ractor_rspec_integration`
-      #   Allow to use Ractor with RSpec. This is an experimental feature and it's not stable.
       #
       # @param config [Hash] Configuration parameters.
       # @param property [Property]
@@ -64,21 +62,12 @@ def setup_for_ractor(config, property, &block)
         if config[:worker] == :ractor
           original_report_on_exception = Thread.report_on_exception
           Thread.report_on_exception = config[:thread_report_on_exception]
-
-          if config[:experimental_ractor_rspec_integration]
-            require "pbt/check/rspec_adapter/integration"
-            class << property
-              include Pbt::Check::RSpecAdapter::PropertyExtension
-            end
-            property.setup_rspec_integration
-          end
         end
 
         yield
       ensure
         if config[:worker] == :ractor
           Thread.report_on_exception = original_report_on_exception
-          property.teardown_rspec_integration if config[:experimental_ractor_rspec_integration]
         end
       end
 
@@ -129,26 +118,11 @@ def run_it_in_ractors(property, runner)
           c.ractor.take
           runner.handle_result(c)
         rescue => e
-          handle_ractor_error(e.cause, c)
+          c.exception = e.cause # Ractor error is wrapped in a Ractor::RemoteError. We need to get the cause.
           runner.handle_result(c)
           break # Ignore the rest of the cases. Just pick up the first failure.
         end
       end
-
-      def handle_ractor_error(cause, c)
-        # Ractor error is wrapped in a Ractor::RemoteError. We need to get the cause.
-        unless defined?(Pbt::Check::RSpecAdapter) && cause.is_a?(Pbt::Check::RSpecAdapter::ExpectationNotMet) # Unknown error.
-          c.exception = cause
-          return
-        end
-
-        # Convert Pbt's custom error to RSpec's error.
-        begin
-          RSpec::Expectations::ExpectationHelper.handle_failure(cause.matcher, cause.custom_message, cause.failure_message_method)
-        rescue RSpec::Expectations::ExpectationNotMetError => e # The class inherits Exception, not StandardError.
-          c.exception = e
-        end
-      end
     end
   end
 end
diff --git a/spec/pbt/check/configuration_spec.rb b/spec/pbt/check/configuration_spec.rb
index f2942f7..134e373 100644
--- a/spec/pbt/check/configuration_spec.rb
+++ b/spec/pbt/check/configuration_spec.rb
@@ -64,8 +64,7 @@
                 worker: :ractor,
                 num_runs: 5,
                 seed: anything,
-                thread_report_on_exception: false,
-                experimental_ractor_rspec_integration: false
+                thread_report_on_exception: false
               }
             )
           end
@@ -99,8 +98,7 @@
                 worker: :ractor,
                 num_runs: 10,
                 seed:,
-                thread_report_on_exception: false,
-                experimental_ractor_rspec_integration: false
+                thread_report_on_exception: false
               }
             )
           end
@@ -130,8 +128,7 @@
                 worker: :none,
                 num_runs: 5,
                 seed: anything,
-                thread_report_on_exception: false,
-                experimental_ractor_rspec_integration: false
+                thread_report_on_exception: false
               }
             )
           end
@@ -165,8 +162,7 @@
                 worker: :none,
                 num_runs: 10,
                 seed:,
-                thread_report_on_exception: false,
-                experimental_ractor_rspec_integration: false
+                thread_report_on_exception: false
               }
             )
           end
@@ -257,53 +253,5 @@
         end
       end
     end
-
-    describe "experimental_ractor_rspec_integration" do
-      it "allows to use RSpec expectation and matchers" do
-        Pbt.assert num_runs: 5, worker: :ractor, experimental_ractor_rspec_integration: true do
-          Pbt.property(Pbt.integer) do |x|
-            expect(x).to be_a(Integer)
-          end
-        end
-
-        Pbt.assert num_runs: 5, worker: :ractor, experimental_ractor_rspec_integration: true do
-          Pbt.property(Pbt.integer, Pbt.integer) do |x, y|
-            expect(x + y).to be_a(Integer)
-          end
-        end
-
-        Pbt.assert num_runs: 5, worker: :ractor, experimental_ractor_rspec_integration: true do
-          Pbt.property(Pbt.array(Pbt.integer, empty: false)) do |nums|
-            expect(nums).to be_a(Array)
-            expect(nums[0]).to be_a(Integer)
-          end
-        end
-
-        Pbt.assert num_runs: 5, worker: :ractor, experimental_ractor_rspec_integration: true do
-          Pbt.property(x: Pbt.integer, y: Pbt.integer) do |x:, y:|
-            expect(x + y).to be_a(Integer)
-          end
-        end
-      end
-
-      it "raises Pbt::PropertyFailure that wraps RSpec's exception when expectation failed" do
-        expect {
-          seed = 135479457171118952930684770951487304295
-          Pbt.assert num_runs: 5, worker: :ractor, seed:, experimental_ractor_rspec_integration: true do
-            Pbt.property(Pbt.integer) do |i|
-              expect(i).to be_a(String)
-            end
-          end
-        }.to raise_error(Pbt::PropertyFailure) do |e|
-          expect(e.message).to include <<~MSG.chomp
-            Property failed after 1 test(s)
-              seed: 135479457171118952930684770951487304295
-              counterexample: 0
-              Shrunk 21 time(s)
-              Got RSpec::Expectations::ExpectationNotMetError: expected 0 to be a kind of String
-          MSG
-        end
-      end
-    end
   end
 end