diff --git a/lib/logtail-rack/http_request.rb b/lib/logtail-rack/http_request.rb
index 7cc3b95..d0db3a3 100755
--- a/lib/logtail-rack/http_request.rb
+++ b/lib/logtail-rack/http_request.rb
@@ -1,3 +1,5 @@
+require "json"
+
 require "logtail-rack/util/encoding"
 
 module Logtail
@@ -26,7 +28,7 @@ def initialize(attributes)
           @service_name = attributes[:service_name]
 
           if @headers
-            @headers_json = Util::Encoding.force_utf8_encoding(@headers).to_json
+            @headers_json = ::JSON.generate(Util::Encoding.force_utf8_encoding(@headers))
           end
         end
 
diff --git a/lib/logtail-rack/http_response.rb b/lib/logtail-rack/http_response.rb
index 4599012..72c1520 100755
--- a/lib/logtail-rack/http_response.rb
+++ b/lib/logtail-rack/http_response.rb
@@ -1,3 +1,5 @@
+require "json"
+
 require "logtail-rack/util/encoding"
 
 module Logtail
@@ -21,7 +23,7 @@ def initialize(attributes)
           @duration_ms = attributes[:duration_ms]
 
           if @headers
-            @headers_json = Util::Encoding.force_utf8_encoding(@headers).to_json
+            @headers_json = ::JSON.generate(Util::Encoding.force_utf8_encoding(@headers))
           end
         end
 
diff --git a/spec/logtail-rack/http_request_spec.rb b/spec/logtail-rack/http_request_spec.rb
index 354eff0..273c761 100755
--- a/spec/logtail-rack/http_request_spec.rb
+++ b/spec/logtail-rack/http_request_spec.rb
@@ -3,4 +3,16 @@
 require "spec_helper"
 
 RSpec.describe Logtail::Integrations::Rack::HTTPRequest do
+  it "build headers_json when to_json raises, as it does with json 3 and ActiveSupport 8.0 or older" do
+    # ActiveSupport up to 8.0 encodes a direct #to_json call itself and passes quirks_mode: to JSON.generate,
+    # which json 3 rejects. JSON.generate calls #to_json with a JSON::State, which ActiveSupport hands to json.
+    allow_any_instance_of(Hash).to receive(:to_json).and_wrap_original do |to_json, *args|
+      raise ArgumentError, "unknown keyword: :quirks_mode" unless args.first.is_a?(JSON::State)
+      to_json.call(*args)
+    end
+
+    http_request = described_class.new(headers: { "Content_Type" => "text/plain", "Accept" => "*/*" })
+
+    expect(http_request.headers_json).to eq('{"Content_Type":"text/plain","Accept":"*/*"}')
+  end
 end
diff --git a/spec/logtail-rack/http_response_spec.rb b/spec/logtail-rack/http_response_spec.rb
index c4a5a49..7755644 100755
--- a/spec/logtail-rack/http_response_spec.rb
+++ b/spec/logtail-rack/http_response_spec.rb
@@ -1,4 +1,16 @@
 require "spec_helper"
 
 RSpec.describe Logtail::Integrations::Rack::HTTPResponse do
+  it "build headers_json when to_json raises, as it does with json 3 and ActiveSupport 8.0 or older" do
+    # ActiveSupport up to 8.0 encodes a direct #to_json call itself and passes quirks_mode: to JSON.generate,
+    # which json 3 rejects. JSON.generate calls #to_json with a JSON::State, which ActiveSupport hands to json.
+    allow_any_instance_of(Hash).to receive(:to_json).and_wrap_original do |to_json, *args|
+      raise ArgumentError, "unknown keyword: :quirks_mode" unless args.first.is_a?(JSON::State)
+      to_json.call(*args)
+    end
+
+    http_response = described_class.new(headers: { "content-type" => "text/plain", "content-length" => "5" }, status: 200)
+
+    expect(http_response.headers_json).to eq('{"content-type":"text/plain","content-length":"5"}')
+  end
 end