diff --git a/configure.in b/configure.in
index b49dffcb59f..00a13253166 100644
--- a/configure.in
+++ b/configure.in
@@ -1667,6 +1667,7 @@ else
   CFLAGS="$OPTIMIZE_CFLAGS -DDBUG_OFF $CFLAGS"
   CXXFLAGS="$OPTIMIZE_CXXFLAGS -DDBUG_OFF $CXXFLAGS"
 fi
+AM_CONDITIONAL(MYSQL_CONF_DEBUG, test "x$with_debug" != "xno")
 
 # Force static compilation to avoid linking problems/get more speed
 AC_ARG_WITH(mysqld-ldflags,
diff --git a/sql/Makefile.am b/sql/Makefile.am
index 8428d6401b5..251fbaa1c9a 100644
--- a/sql/Makefile.am
+++ b/sql/Makefile.am
@@ -117,9 +117,14 @@ DEFS =			-DMYSQL_SERVER \
 
 BUILT_SOURCES =		sql_yacc.cc sql_yacc.h lex_hash.h
 EXTRA_DIST =		$(BUILT_SOURCES)
-DISTCLEANFILES =        lex_hash.h
+DISTCLEANFILES =        lex_hash.h sql_yacc.output
+
 AM_YFLAGS =		-d
 
+if MYSQL_CONF_DEBUG
+AM_YFLAGS +=		--debug --verbose
+endif
+
 mysql_tzinfo_to_sql.cc:
 	rm -f mysql_tzinfo_to_sql.cc
 	@LN_CP_F@ $(srcdir)/tztime.cc mysql_tzinfo_to_sql.cc
diff --git a/sql/sql_parse.cc b/sql/sql_parse.cc
index 72098fb83e4..ceda7507d23 100644
--- a/sql/sql_parse.cc
+++ b/sql/sql_parse.cc
@@ -5776,6 +5776,26 @@ void mysql_init_multi_delete(LEX *lex)
   lex->query_tables_last= &lex->query_tables;
 }
 
+#ifndef DBUG_OFF
+static void turn_parser_debug_on()
+{
+  /*
+     MYSQLdebug is in sql/sql_yacc.cc, in bison generated code.
+     Turning this option on is **VERY** verbose, and should be
+     used when investigating a syntax error problem only.
+
+     The syntax to run with bison traces is as follows :
+     - Starting a server manually :
+       mysqld --debug="d,parser_debug" ...
+     - Running a test :
+       mysql-test-run.pl --mysqld="--debug=d,parser_debug" ...
+
+     The result will be in the process stderr (var/log/master.err)
+   */
+  extern int MYSQLdebug;
+  MYSQLdebug= 1;
+}
+#endif
 
 /*
   When you modify mysql_parse(), you may need to mofify
@@ -5785,6 +5805,9 @@ void mysql_init_multi_delete(LEX *lex)
 void mysql_parse(THD *thd, char *inBuf, uint length)
 {
   DBUG_ENTER("mysql_parse");
+
+  DBUG_EXECUTE_IF("parser_debug", turn_parser_debug_on(););
+
   mysql_init_query(thd, (uchar*) inBuf, length);
   if (query_cache_send_result_to_client(thd, inBuf, length) <= 0)
   {