diff --git a/lib/filelib.php b/lib/filelib.php
index b893cf22f98..69d8da0e18d 100644
--- a/lib/filelib.php
+++ b/lib/filelib.php
@@ -2683,7 +2683,8 @@ class curl {
     public $emulateredirects = null;
 
     /** @var array cURL options */
-    private $options;
+    protected $options;
+
     /** @var string Proxy host */
     private $proxy_host = '';
     /** @var string Proxy auth */
@@ -2975,7 +2976,7 @@ class curl {
      * @param array $options
      * @return resource The curl handle
      */
-    private function apply_opt($curl, $options) {
+    protected function apply_opt($curl, $options) {
         // Clean up
         $this->cleanopt();
         // set cookie
@@ -3004,15 +3005,36 @@ class curl {
         }
 
         $this->setopt($options);
-        // reset before set options
+
+        // Reset before set options.
         curl_setopt($curl, CURLOPT_HEADERFUNCTION, array(&$this,'formatHeader'));
-        // set headers
+
+        // Setting the User-Agent based on options provided.
+        $useragent = '';
+
+        if (!empty($options['CURLOPT_USERAGENT'])) {
+            $useragent = $options['CURLOPT_USERAGENT'];
+        } else if (!empty($this->options['CURLOPT_USERAGENT'])) {
+            $useragent = $this->options['CURLOPT_USERAGENT'];
+        } else {
+            $useragent = 'MoodleBot/1.0';
+        }
+
+        // Set headers.
         if (empty($this->header)) {
             $this->setHeader(array(
-                'User-Agent: MoodleBot/1.0',
+                'User-Agent: ' . $useragent,
                 'Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7',
                 'Connection: keep-alive'
                 ));
+        } else if (!in_array('User-Agent: ' . $useragent, $this->header)) {
+            // Remove old User-Agent if one existed.
+            // We have to partial search since we don't know what the original User-Agent is.
+            if ($match = preg_grep('/User-Agent.*/', $this->header)) {
+                $key = array_keys($match)[0];
+                unset($this->header[$key]);
+            }
+            $this->setHeader(array('User-Agent: ' . $useragent));
         }
         curl_setopt($curl, CURLOPT_HTTPHEADER, $this->header);
 
diff --git a/lib/tests/filelib_test.php b/lib/tests/filelib_test.php
index cab417d00c2..f74e655f391 100644
--- a/lib/tests/filelib_test.php
+++ b/lib/tests/filelib_test.php
@@ -878,4 +878,80 @@ EOF;
         $this->assertEquals('image', $mimeinfo['png']['string']);
         $this->assertEquals(true, $mimeinfo['txt']['defaulticon']);
     }
+
+    /**
+     * Test curl agent settings.
+     */
+    public function test_curl_useragent() {
+        $curl = new curl_extended();
+        $options = $curl->get_options();
+        $this->assertNotEmpty($options);
+
+        $curl->call_apply_opt($options);
+        $this->assertTrue(in_array('User-Agent: MoodleBot/1.0', $curl->header));
+        $this->assertFalse(in_array('User-Agent: Test/1.0', $curl->header));
+
+        $options['CURLOPT_USERAGENT'] = 'Test/1.0';
+        $curl->call_apply_opt($options);
+        $this->assertTrue(in_array('User-Agent: Test/1.0', $curl->header));
+        $this->assertFalse(in_array('User-Agent: MoodleBot/1.0', $curl->header));
+
+        $curl->set_option('CURLOPT_USERAGENT', 'AnotherUserAgent/1.0');
+        $curl->call_apply_opt();
+        $this->assertTrue(in_array('User-Agent: AnotherUserAgent/1.0', $curl->header));
+        $this->assertFalse(in_array('User-Agent: Test/1.0', $curl->header));
+
+        $curl->set_option('CURLOPT_USERAGENT', 'AnotherUserAgent/1.1');
+        $options = $curl->get_options();
+        $curl->call_apply_opt($options);
+        $this->assertTrue(in_array('User-Agent: AnotherUserAgent/1.1', $curl->header));
+        $this->assertFalse(in_array('User-Agent: AnotherUserAgent/1.0', $curl->header));
+
+        $curl->unset_option('CURLOPT_USERAGENT');
+        $curl->call_apply_opt();
+        $this->assertTrue(in_array('User-Agent: MoodleBot/1.0', $curl->header));
+    }
+}
+
+/**
+ * Test-specific class to allow easier testing of curl functions.
+ * 
+ * @copyright 2015 Dave Cooper 
+ * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class curl_extended extends curl {
+    /**
+     * Accessor for options array.
+     */
+    public function get_options() {
+        return $this->options;
+    }
+
+    /**
+     * Setter for options array.
+     * @param string $option
+     * @param string $value
+     */
+    public function set_option($option, $value) {
+        $this->options[$option] = $value;
+    }
+
+    /**
+     * Unsets an option on the curl object
+     * @param string $option
+     */
+    public function unset_option($option) {
+        unset($this->options[$option]);
+    }
+
+    /**
+     * Wrapper to access the curl::apply_opt() function
+     *
+     * @param array $options
+     * @return resource The curl handle
+     */
+    public function call_apply_opt($options = null) {
+        $ch = curl_init();
+        return $this->apply_opt($ch, $options);
+    }
 }