diff --git a/src/Client.php b/src/Client.php
index 11f55a8..bd6a9c3 100644
--- a/src/Client.php
+++ b/src/Client.php
@@ -4,6 +4,7 @@
 use DateTime;
 
 const VERSION = "1.2.1-dev";
+const CA_BUNDLE_VERSION = "1.0";
 const INITIAL_BACKOFF_SECONDS = 1;
 const MAX_BACKOFF_SECONDS = 32;
 const BACKOFF_FACTOR = 2;
@@ -240,7 +241,10 @@ public function apiCall($method, $path, $params, $additional_headers = [])
         }
 
         $headers["Date"] = $now;
-        $headers["User-Agent"] = "duo_api_php/" . VERSION;
+        $ca_pinning_status = (!empty($this->options["disable_ca_pinning"])) ? "disabled" : "enabled";
+        $headers["User-Agent"] = "duo_api_php/" . VERSION
+            . " ca_bundle/" . CA_BUNDLE_VERSION
+            . " (ca_pinning=" . $ca_pinning_status . ")";
         $headers["Authorization"] = self::signParameters(
             $method,
             $this->host,
diff --git a/tests/Unit/ClientTest.php b/tests/Unit/ClientTest.php
index 416f127..b5adefd 100644
--- a/tests/Unit/ClientTest.php
+++ b/tests/Unit/ClientTest.php
@@ -493,9 +493,39 @@ public function testUserAgent()
             $this->anything(),
             $this->anything(),
             $this->callback(function($headers) {
-                $version = "duo_api_php/" . \DuoAPI\VERSION;
+                $expected = "duo_api_php/" . \DuoAPI\VERSION
+                    . " ca_bundle/" . \DuoAPI\CA_BUNDLE_VERSION
+                    . " (ca_pinning=enabled)";
                 $this->assertArrayHasKey("User-Agent", $headers);
-                $this->assertEquals($headers["User-Agent"], $version);
+                $this->assertEquals($expected, $headers["User-Agent"]);
+                return true;
+            }),
+            $this->anything()
+        );
+        $response = $client->apiCall("GET", "/foo/bar", []);
+    }
+
+    public function testUserAgentWithCaPinningDisabled()
+    {
+        $success_resp = [
+            "success" => true,
+            "response" => "not rate limited",
+            "http_status_code" => 200,
+        ];
+
+        $response = [$success_resp];
+
+        $client = self::getMockedClient("Client", $response, $paged = true);
+        $client->disableCaPinning();
+        $this->mocked_curl_requester->method('execute')->with(
+            $this->anything(),
+            $this->anything(),
+            $this->callback(function($headers) {
+                $expected = "duo_api_php/" . \DuoAPI\VERSION
+                    . " ca_bundle/" . \DuoAPI\CA_BUNDLE_VERSION
+                    . " (ca_pinning=disabled)";
+                $this->assertArrayHasKey("User-Agent", $headers);
+                $this->assertEquals($expected, $headers["User-Agent"]);
                 return true;
             }),
             $this->anything()