Question: Error during the reconfiguration of the Apache files in Plesk: Invalid command 'RequestHeader', perhaps misspelled or defined by a module not included in the server configuration
Symptoms
Execution of the plesk repair web command returns the next error message:
AH00526: Syntax error on line 117 of /etc/apache2/plesk.conf.d/server.conf:
Invalid command 'RequestHeader', perhaps misspelled or defined by a module not included in the server configuration
Cause
All Apache modules are disabled.
Resolution
1.Log into Plesk
2.Go to Tools & Settings > Apache Web Server
3.Enable modules as on the screenshot below and press the OK button to apply the changes:
(https://pix.cobrasoft.org/images/2025/08/23/image.png)
4.Log into the server via SSH
5.Execute the command below to repair the Apache configuration:
#plesk repair web