diff --git a/.circleci/config.yml b/.circleci/config.yml
index 5400178e..1269bdda 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -279,7 +279,7 @@ workflows:
                 - "3.2"
                 - "3.3"
                 - "3.4"
-                - "3.5.0-preview1"
+                - "4.0"
   libraries_ruby_31_32:
     jobs:
       - test_apprisal:
@@ -304,7 +304,7 @@ workflows:
               ruby_version:
                 - "3.3"
                 - "3.4"
-                - "3.5.0-preview1"
+                - "4.0"
             # Currently compiling the native extensions for `grpc`
             # exceeds an internal RAM and/or CPU limit of CircleCI executor,
             # and the job gets terminated with:
@@ -314,7 +314,7 @@ workflows:
             # on https://rubygems.org/gems/grpc/versions
             exclude:
             - stack: base
-              ruby_version: "3.5.0-preview1"
+              ruby_version: "4.0"
               gemfile: "./gemfiles/grpc_10.gemfile"
   rails_ruby_31_35:
     jobs:
@@ -335,7 +335,7 @@ workflows:
                 - "3.2"
                 - "3.3"
                 - "3.4"
-                - "3.5.0-preview1"             
+                - "4.0"             
   rails8_ruby_33_35:
     jobs:
       - test_apprisal:
@@ -369,7 +369,7 @@ workflows:
                 - "3.1"
                 - "3.2"
                 - "3.3"
-                - "3.5.0-preview1"
+                - "4.0"
   report_coverage:
     jobs:
       - report_coverage
diff --git a/instana.gemspec b/instana.gemspec
index 08715f53..6ccbaa3c 100644
--- a/instana.gemspec
+++ b/instana.gemspec
@@ -48,5 +48,6 @@ Gem::Specification.new do |spec|
   spec.add_runtime_dependency('sys-proctable', '>= 1.2.2')
   spec.add_runtime_dependency('opentelemetry-api', '~> 1.4')
   spec.add_runtime_dependency('opentelemetry-common')
+  spec.add_runtime_dependency('cgi')
   spec.add_runtime_dependency('oj', '>=3.0.11') unless RUBY_PLATFORM =~ /java/i
 end
diff --git a/lib/instana/trace/span.rb b/lib/instana/trace/span.rb
index 52543bed..c8d64ddf 100644
--- a/lib/instana/trace/span.rb
+++ b/lib/instana/trace/span.rb
@@ -83,14 +83,14 @@ def add_stack(limit: 30, stack: Kernel.caller)
 
       @attributes[:stack] = stack
                             .map do |call|
-        file, line, *method = call.split(':')
-
-        {
-          c: file,
-          n: line,
-          m: method.join(' ')
-        }
-      end.take(limit > 40 ? 40 : limit)
+                              file, line, *method = call.split(':')
+
+                              {
+                                c: file,
+                                n: line,
+                                m: method.join(' ')
+                              }
+      end.take([limit, 40].min)
     end
 
     # Log an error into the span
diff --git a/test/instrumentation/rest_client_test.rb b/test/instrumentation/rest_client_test.rb
index 1ae33a29..0ec6b0d0 100644
--- a/test/instrumentation/rest_client_test.rb
+++ b/test/instrumentation/rest_client_test.rb
@@ -7,7 +7,7 @@
 class RestClientTest < Minitest::Test
   def setup
     # See https://github.com/rest-client/rest-client/issues/612
-    OpenSSL::SSL::SSLContext::DEFAULT_PARAMS[:ciphers] = OpenSSL::SSL::SSLContext.new.ciphers
+    OpenSSL::SSL::SSLContext::DEFAULT_PARAMS[:ciphers] = OpenSSL::SSL::SSLContext.new.ciphers if Gem::Version.new(RUBY_VERSION) < Gem::Version.new('4.0')
   end
 
   def teardown