Fatal error: Undefined Constant

I am receiving the following fatal error:

Fatal error: Uncaught Error: Undefined constant “YellowTree\GeoipDetect\DataSources\Fastah\CURL_HTTP_VERSION_1_1” in /home/_website/public_html/wp-content/plugins/geoip-detect/data-sources/fastah.php:280 Stack trace: #0 /home/_website/public_html/wp-content/plugins/geoip-detect/geoip-detect.php(97): include_once() #1 /home/_website/public_html/wp-settings.php(597): include_once(‘/home/_website/…’) #2 /home/_website/public_html/wp-config.php(95): require_once(‘/home/_website/…’) #3 /home/_website/public_html/wp-load.php(50): require_once(‘/home/_website/…’) #4 /home/_website/public_html/wp-admin/admin.php(35): require_once(‘/home/_website/…’) #5 /home/_website/public_html/wp-admin/index.php(10): require_once(‘/home/_website/…’) #6 {main} thrown in /home/_website/public_html/wp-content/plugins/geoip-detect/data-sources/fastah.php on line 280