Title: Fatal error: Undefined Constant
Last modified: September 8, 2026

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# Fatal error: Undefined Constant

 *  [IIIImpulse](https://wordpress.org/support/users/iiiimpulse/)
 * (@iiiimpulse)
 * [1 week, 1 day ago](https://wordpress.org/support/topic/fatal-error-undefined-constant-3/)
 * 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**

Viewing 1 replies (of 1 total)

 *  Plugin Author [Benjamin Pick](https://wordpress.org/support/users/benjaminpick/)
 * (@benjaminpick)
 * [1 week ago](https://wordpress.org/support/topic/fatal-error-undefined-constant-3/#post-19015878)
 * Very Interesting. It seems to be an old version of the libcurl library. Please
   try if the 5.6.5-beta version fixes it: 
   [https://github.com/yellowtree/geoip-detect/wiki/Beta-Testing](https://github.com/yellowtree/geoip-detect/wiki/Beta-Testing)

Viewing 1 replies (of 1 total)

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 * 1 reply
 * 2 participants
 * Last reply from: [Benjamin Pick](https://wordpress.org/support/users/benjaminpick/)
 * Last activity: [1 week ago](https://wordpress.org/support/topic/fatal-error-undefined-constant-3/#post-19015878)
 * Status: not resolved