diff --git a/src/libpcp/src/.gitignore b/src/libpcp/src/.gitignore
index fdaa281bf4..45335749a6 100644
--- a/src/libpcp/src/.gitignore
+++ b/src/libpcp/src/.gitignore
@@ -8,6 +8,7 @@ jsonsl.c
 sha256.h
 sha256.c
 getdate.h
+getdate.y
 getdate.tab.?
 derive_parser.y
 derive_parser.output
diff --git a/src/libpcp_web/src/.gitignore b/src/libpcp_web/src/.gitignore
index 2f85803791..598196be02 100644
--- a/src/libpcp_web/src/.gitignore
+++ b/src/libpcp_web/src/.gitignore
@@ -19,6 +19,7 @@ crc16.h
 siphash.c
 http_parser.c
 http_parser.h
+query_parser.y
 query_parser.tab.c
 query_parser.tab.h
 libpcp_web.dll
diff --git a/src/libpcp_web/src/GNUmakefile b/src/libpcp_web/src/GNUmakefile
index 7da7d8e68c..68ace6f51c 100644
--- a/src/libpcp_web/src/GNUmakefile
+++ b/src/libpcp_web/src/GNUmakefile
@@ -59,7 +59,7 @@ XFILES += fnmatch.c fnmatch.h
 LCFLAGS += -I.
 endif
 
-LDIRT = $(XFILES) $(YFILES:%.y=%.tab.?)
+LDIRT = $(XFILES) $(YFILES:%.y=%.tab.?) query_parser.y
 LCFLAGS += $(C99_CFLAGS) -DJSMN_PARENT_LINKS=1 -DJSMN_STRICT=1 -DHTTP_PARSER_STRICT=0 -Ideps
 
 ifeq "$(HAVE_LIBUV)" "true"
@@ -138,6 +138,9 @@ $(HIREDIS_CLUSTER_XFILES):
 query_parser.tab.h query_parser.tab.c: query_parser.y query.h
 	$(YACC) -d -b `basename $< .y` $<
 
+query_parser.y: query_parser.y.in fix_query_parser_y
+	./fix_query_parser_y
+
 default_pcp:	default
 
 install_pcp:	install
diff --git a/src/libpcp_web/src/fix_query_parser_y b/src/libpcp_web/src/fix_query_parser_y
new file mode 100755
index 0000000000..7cf03bcb2d
--- /dev/null
+++ b/src/libpcp_web/src/fix_query_parser_y
@@ -0,0 +1,56 @@
+#!/bin/sh
+# Handle Bison version issues for query_parser.y
+#
+
+b_version=`bison --version | sed -n -e '/^bison/s/.*)  *//p'`
+
+if [ -z "$b_version" ]
+then
+    echo "Arrgh ... cannot get bison version from ..."
+    bison --version
+    exit 1
+fi
+
+if [ ! -f query_parser.y.in ]
+then
+    echo "Arrgh ... cannot find query_parser.y.in"
+    exit 1
+fi
+
+rm -f query_parser.y
+cat <<End-of-File >query_parser.y
+/*
+ * DO NOT EDIT THIS FILE ... CHANGES HERE WILL BE LOST
+ *
+ * This file created from query_parser.y.in (make changes there!)
+ * by fix_query_parser_y on ${PACKAGE_BUILD_DATE:-`date`}.
+ */
+
+End-of-File
+
+# From the bison CHANGELOG
+# 2012-10-26
+#	version 2.6.4
+# 2012-10-25
+# 	src/parse-gram.y (%pure-parser, %name-prefix): Replace with...
+#	 	(%define api.pure, %define api.prefix)
+#
+case "$b_version"
+in
+    2.[0-5]*|2.6.[0-3])
+	sed -e 's/^PUT-PURE-DECL-HERE.*/%pure-parser/' <query_parser.y.in >>query_parser.y
+	;;
+    2.6.[4-9]|2.[7-9]*|3.*)
+	sed -e 's/^PUT-PURE-DECL-HERE.*/%define api.pure full/' <query_parser.y.in >>query_parser.y
+	;;
+    *)
+	rm -f query_parser.y
+	echo "Arrgh ... don't know what to do with bison version $b_version"
+	exit 1
+	;;
+esac
+
+chmod a-w query_parser.y
+
+exit 0
+
diff --git a/src/libpcp_web/src/query_parser.y b/src/libpcp_web/src/query_parser.y.in
similarity index 99%
rename from src/libpcp_web/src/query_parser.y
rename to src/libpcp_web/src/query_parser.y.in
index 5292ac3522..fb47db5579 100644
--- a/src/libpcp_web/src/query_parser.y
+++ b/src/libpcp_web/src/query_parser.y.in
@@ -69,15 +69,7 @@ static char *n_type_c(int);
 static char *l_type_str(int);
 %}
 
-/*
- * seems like the %define variant is more bisonesque, while the
- * %pure-parser maybe a yaccism that bison silently accepts ...
- * using the %define makes "deprecated directive" warnings go
- * away on some platforms - kenj Oct 2019
- * old yacc declaration was
- * %pure-parser
- */
-%define api.pure
+PUT-PURE-DECL-HERE ... see GNUmakefile and fix_query_parser_y
 
 %parse-param { PARSER *lp }
 %lex-param { PARSER *lp }