diff --git a/config/initializers/web_push.rb b/config/initializers/web_push.rb
index 6914dae22..4487268f5 100644
--- a/config/initializers/web_push.rb
+++ b/config/initializers/web_push.rb
@@ -20,7 +20,8 @@ module WebPush::PersistentRequest
     endpoint_ip = @options[:endpoint_ip]
 
     if endpoint_ip
-      http = Net::HTTP.new(uri.host, uri.port, ipaddr: endpoint_ip)
+      http = Net::HTTP.new(uri.host, uri.port)
+      http.ipaddr = endpoint_ip
       http.use_ssl = true
       http.ssl_timeout = @options[:ssl_timeout] unless @options[:ssl_timeout].nil?
       http.open_timeout = @options[:open_timeout] unless @options[:open_timeout].nil?
diff --git a/test/lib/web_push/persistent_request_test.rb b/test/lib/web_push/persistent_request_test.rb
new file mode 100644
index 000000000..2cf8a6c7c
--- /dev/null
+++ b/test/lib/web_push/persistent_request_test.rb
@@ -0,0 +1,26 @@
+require "test_helper"
+
+class WebPush::PersistentRequestTest < ActiveSupport::TestCase
+  PUBLIC_TEST_IP = "142.250.185.206"
+  ENDPOINT = "https://fcm.googleapis.com/fcm/send/test123"
+
+  test "pins connection to endpoint_ip" do
+    request = stub_request(:post, ENDPOINT)
+      .with(ipaddr: PUBLIC_TEST_IP)
+      .to_return(status: 201)
+
+    notification = WebPush::Notification.new(
+      title: "Test",
+      body: "Test notification",
+      path: "/test",
+      badge: 0,
+      endpoint: ENDPOINT,
+      endpoint_ip: PUBLIC_TEST_IP,
+      p256dh_key: "BNcRdreALRFXTkOOUHK1EtK2wtaz5Ry4YfYCA_0QTpQtUbVlUls0VJXg7A8u-Ts1XbjhazAkj7I99e8QcYP7DkM",
+      auth_key: "tBHItJI5svbpez7KI4CCXg"
+    )
+    notification.deliver
+
+    assert_requested request
+  end
+end
diff --git a/test/test_helper.rb b/test/test_helper.rb
index 14893b030..b1f813761 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -3,6 +3,7 @@ require_relative "../config/environment"
 
 require "rails/test_help"
 require "webmock/minitest"
+require_relative "webmock_ipaddr_extension"
 require "vcr"
 require "mocha/minitest"
 require "turbo/broadcastable/test_helper"
diff --git a/test/webmock_ipaddr_extension.rb b/test/webmock_ipaddr_extension.rb
new file mode 100644
index 000000000..874654f87
--- /dev/null
+++ b/test/webmock_ipaddr_extension.rb
@@ -0,0 +1,44 @@
+# Extends WebMock to support ipaddr matching for testing IP pinning.
+#
+# Usage:
+#   stub_request(:post, "https://example.com/push")
+#     .with(ipaddr: "93.184.216.34")
+#     .to_return(status: 201)
+#
+# If the HTTP connection's ipaddr doesn't match, the stub won't match and
+# WebMock will raise an error about an unregistered request.
+
+module WebMock
+  class RequestSignature
+    attr_accessor :ipaddr
+  end
+
+  module RequestPatternIpaddrExtension
+    attr_accessor :ipaddr_pattern
+
+    def assign_options(options)
+      options = options.dup
+      @ipaddr_pattern = options.delete(:ipaddr) || options.delete("ipaddr")
+      super(options)
+    end
+
+    def matches?(request_signature)
+      super && ipaddr_matches?(request_signature)
+    end
+
+    private
+      def ipaddr_matches?(request_signature)
+        @ipaddr_pattern.nil? || @ipaddr_pattern == request_signature.ipaddr
+      end
+  end
+
+  RequestPattern.prepend RequestPatternIpaddrExtension
+
+  module NetHTTPUtilityIpaddrExtension
+    def request_signature_from_request(net_http, request, body = nil)
+      super.tap { |signature| signature.ipaddr = net_http.ipaddr }
+    end
+  end
+
+  NetHTTPUtility.singleton_class.prepend NetHTTPUtilityIpaddrExtension
+end