diff --git a/doc/scripts/clint.sh b/doc/scripts/clint.sh
index c3f5fa0..a1379d6 100755
--- a/doc/scripts/clint.sh
+++ b/doc/scripts/clint.sh
@@ -123,7 +123,7 @@ while getopts "cO:P:" name; do
 			export "${OPTARG%%=*}"="${OPTARG#*=}"
 			;;
 		P)
-			#XXX ignored for compatibility
+			CPPFLAGS="$CPPFLAGS -I$OPTARG/include"
 			;;
 		?)
 			_usage