diff --git a/common.mk b/common.mk
index d6e4d6acd7..f740f93af6 100755
--- a/common.mk
+++ b/common.mk
@@ -851,6 +851,7 @@ PHONY:
 {$(srcdir)}.y.c:
 	$(ECHO) generating $@
 	$(Q)$(BASERUBY) $(srcdir)/tool/id2token.rb --path-separator=.$(PATH_SEPARATOR)./ --vpath=$(VPATH) id.h $(SRC_FILE) > parse.tmp.y
+	$(Q)$(BASERUBY) $(srcdir)/tool/pure_parser.rb parse.tmp.y $(YACC)
 	$(Q)$(YACC) -d $(YFLAGS) -o y.tab.c parse.tmp.y
 	$(Q)$(RM) parse.tmp.y
 	$(Q)sed -f $(srcdir)/tool/ytab.sed -e "/^#/s|parse\.tmp\.[iy]|$(SRC_FILE)|" -e "/^#/s!y\.tab\.c!$@!" y.tab.c > $@.new
diff --git a/parse.y b/parse.y
index d76d3b2562..665067d3e6 100644
--- a/parse.y
+++ b/parse.y
@@ -910,7 +910,7 @@ static void token_info_warn(struct parser_params *p, const char *token, token_in
 %}
 
 %expect 0
-%pure-parser
+%define api.pure
 %lex-param {struct parser_params *p}
 %parse-param {struct parser_params *p}
 %initial-action
diff --git a/tool/pure_parser.rb b/tool/pure_parser.rb
new file mode 100755
index 0000000000..20d71079a0
--- /dev/null
+++ b/tool/pure_parser.rb
@@ -0,0 +1,15 @@
+#!/usr/bin/ruby -pi
+BEGIN {
+  require_relative 'colorize'
+
+  colorize = Colorize.new
+  file = ARGV.shift
+  unless /\Abison .* (\d+)\.\d+/ =~ IO.popen(ARGV+%w[--version], &:read)
+    puts colorize.fail("not bison")
+    exit
+  end
+  exit if $1.to_i >= 3
+  ARGV.clear
+  ARGV.push(file)
+}
+$_.sub!(/^%define\s+api\.pure/, '%pure-parser')