diff --git a/ext/coverage/coverage.c b/ext/coverage/coverage.c
index 1519b559cdafc1..74d9f3ea4655fe 100644
--- a/ext/coverage/coverage.c
+++ b/ext/coverage/coverage.c
@@ -352,7 +352,6 @@ rb_coverage_peek_result(VALUE klass)
     if (!RTEST(coverages)) {
         rb_raise(rb_eRuntimeError, "coverage measurement is not enabled");
     }
-    OBJ_WB_UNPROTECT(coverages);
 
     rb_hash_foreach(coverages, coverage_peek_result_i, ncoverages);
 
diff --git a/id_table.c b/id_table.c
index eb8477237ea622..4629af553505b7 100644
--- a/id_table.c
+++ b/id_table.c
@@ -353,7 +353,7 @@ const rb_data_type_t rb_managed_id_table_type = {
     .wrap_struct_name = "VM/managed_id_table",
     .function = {
         .dmark = NULL, // Nothing to mark
-        .dfree = (RUBY_DATA_FUNC)managed_id_table_free,
+        .dfree = managed_id_table_free,
         .dsize = managed_id_table_memsize,
     },
     .flags = RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED | RUBY_TYPED_EMBEDDABLE,
diff --git a/lib/cgi.rb b/lib/cgi.rb
index b041c1bed13b1c..bb306d2e0644cf 100644
--- a/lib/cgi.rb
+++ b/lib/cgi.rb
@@ -2,6 +2,6 @@
 
 require "cgi/escape"
 warn <<-WARNING, uplevel: Gem::BUNDLED_GEMS.uplevel if $VERBOSE
-CGI library is removed from Ruby 3.5. Please use cgi/escape instead for CGI.escape and CGI.unescape features.
+CGI library is removed from Ruby 4.0. Please use cgi/escape instead for CGI.escape and CGI.unescape features.
 If you need to use the full features of CGI library, Please install cgi gem.
 WARNING
diff --git a/lib/cgi/util.rb b/lib/cgi/util.rb
index 389a04acd21f05..50a2e91665e000 100644
--- a/lib/cgi/util.rb
+++ b/lib/cgi/util.rb
@@ -2,6 +2,6 @@
 
 require "cgi/escape"
 warn <<-WARNING, uplevel: Gem::BUNDLED_GEMS.uplevel if $VERBOSE
-CGI::Util is removed from Ruby 3.5. Please use cgi/escape instead for CGI.escape and CGI.unescape features.
+CGI::Util is removed from Ruby 4.0. Please use cgi/escape instead for CGI.escape and CGI.unescape features.
 If you are using CGI.parse, please install and use the cgi gem instead.
 WARNING
diff --git a/lib/erb/util.rb b/lib/erb/util.rb
index 9c3d186edefb62..adeb695aa81fec 100644
--- a/lib/erb/util.rb
+++ b/lib/erb/util.rb
@@ -2,8 +2,8 @@
 
 # Load CGI.escapeHTML and CGI.escapeURIComponent.
 # CRuby:
-#   cgi.gem v0.1.0+ (Ruby 2.7-3.4) and Ruby 3.5+ stdlib have 'cgi/escape' and CGI.escapeHTML.
-#   cgi.gem v0.3.3+ (Ruby 3.2-3.4) and Ruby 3.5+ stdlib have CGI.escapeURIComponent.
+#   cgi.gem v0.1.0+ (Ruby 2.7-3.4) and Ruby 4.0+ stdlib have 'cgi/escape' and CGI.escapeHTML.
+#   cgi.gem v0.3.3+ (Ruby 3.2-3.4) and Ruby 4.0+ stdlib have CGI.escapeURIComponent.
 # JRuby: cgi.gem has a Java extension 'cgi/escape'.
 # TruffleRuby: lib/truffle/cgi/escape.rb requires 'cgi/util'.
 require 'cgi/escape'
diff --git a/test/openssl/test_ssl.rb b/test/openssl/test_ssl.rb
index e700e53e3b58c0..5082dadd1b7971 100644
--- a/test/openssl/test_ssl.rb
+++ b/test/openssl/test_ssl.rb
@@ -2325,12 +2325,12 @@ def test_export_keying_material
     end
   end
 
-  # OpenSSL::Buffering requires $/ accessible from non-main Ractors (Ruby 3.5)
+  # OpenSSL::Buffering requires $/ accessible from non-main Ractors (Ruby 4.0)
   # https://bugs.ruby-lang.org/issues/21109
   #
   # Hangs on Windows
   # https://bugs.ruby-lang.org/issues/21537
-  if respond_to?(:ractor) && RUBY_VERSION >= "3.5" && RUBY_PLATFORM !~ /mswin|mingw/
+  if respond_to?(:ractor) && RUBY_VERSION >= "4.0" && RUBY_PLATFORM !~ /mswin|mingw/
     ractor
     def test_ractor_client
       start_server { |port|