diff --git a/configure.ac b/configure.ac
index 96f5079..6caba30 100644
--- a/configure.ac
+++ b/configure.ac
@@ -54,7 +54,7 @@ AC_SUBST(NEEDED)
 
 # Find the xcb-proto protocol descriptions
 AC_MSG_CHECKING(XCBPROTO_XCBINCLUDEDIR)
-XCBPROTO_XCBINCLUDEDIR=`$PKG_CONFIG --variable=xcbincludedir xcb-proto`
+XCBPROTO_XCBINCLUDEDIR=${ROOT}`$PKG_CONFIG --variable=xcbincludedir xcb-proto`
 AC_MSG_RESULT($XCBPROTO_XCBINCLUDEDIR)
 AC_SUBST(XCBPROTO_XCBINCLUDEDIR)