diff --git a/src/bison.sh b/src/bison.sh
index e7060801..0da66e3d 100755
--- a/src/bison.sh
+++ b/src/bison.sh
@@ -3,23 +3,20 @@ set -e
 
 BISONFLAGS=-Wall
 
-readonly BISON_VER=$(bison -V)
+readonly BISON_MAJOR=$(bison -V | sed -E 's/^.+ ([0-9]+)\..*$/\1/g;q')
+readonly BISON_MINOR=$(bison -V | sed -E 's/^.+ [0-9]+\.([0-9]+)\..*$/\1/g;q')
+
 add_flag () {
-	if awk <<<"$BISON_VER" -v major="$1" -v minor="$2" '
-	/^bison.*[0-9]+(\.[0-9]+)(\.[0-9]+)?$/ {
-		match($0, /[0-9]+(\.[0-9]+)(\.[0-9]+)?$/);
-		split(substr($0, RSTART), ver, ".");
-		if (ver[1] == major && ver[2] >= minor) { exit 0 } else { exit 1 }
-	}'; then
-		BISONFLAGS="-D$3 $BISONFLAGS"
+	if [[ "$BISON_MAJOR" -eq "$1" && "$BISON_MINOR" -ge "$2" ]]; then
+		BISONFLAGS="$BISONFLAGS -D$3"
 	fi
 }
 
-add_flag 3 5 api.token.raw=true
-add_flag 3 6 parse.error=detailed
 add_flag 3 0 parse.error=verbose
 add_flag 3 0 parse.lac=full
 add_flag 3 0 lr.type=ielr
+add_flag 3 5 api.token.raw=true
+add_flag 3 6 parse.error=detailed
 
 echo "BISONFLAGS=$BISONFLAGS"