--- a/lib/xpp/CMakeLists.txt	2026-10-19 16:49:13.128163451 +0200
+++ b/lib/xpp/CMakeLists.txt	2026-10-19 16:49:13.129848510 +0200
@@ -10,7 +10,9 @@ find_package(PkgConfig)
 pkg_check_modules(XCBPROTO REQUIRED xcb-proto)
 
 # Store the location of the proto xml files inside XCBPROTO_XCBINCLUDEDIR
-pkg_get_variable(XCBPROTO_XCBINCLUDEDIR xcb-proto xcbincludedir)
+if(NOT XCBPROTO_XCBINCLUDEDIR)
+  pkg_get_variable(XCBPROTO_XCBINCLUDEDIR xcb-proto xcbincludedir)
+endif()
 
 # Search for a python interpreter, if the user didn't specify any
 if(NOT PYTHON_EXECUTABLE)