--- a/src/kash/Makefile.kmk	2022-11-12 16:42:14.195927909 +0200
+++ b/src/kash/Makefile.kmk	2022-11-12 17:09:46.212159615 +0200
@@ -210,8 +210,11 @@
 kash_USES = lex yacc
 kash_LEXTOOL = FLEX
 kash_LEXFLAGS = -8
-#kash_YACCTOOL = BISON
+ifneq (,$(shell bison -V))
+kash_YACCTOOL = BISON
+else
 kash_YACCTOOL = YACC
+endif
 kash_YACCFLAGS = -ld
 kash_SOURCES += \
 	arith.y \