diff --git a/src/backend/regex/regcomp.c b/src/backend/regex/regcomp.c
index cb4dd2d3395..03133f4a048 100644
--- a/src/backend/regex/regcomp.c
+++ b/src/backend/regex/regcomp.c
@@ -944,7 +944,7 @@ parseqatom(struct vars * v,
 			EMPTYARC(lp, s);
 			EMPTYARC(s2, rp);
 			NOERR();
-			atom = parse(v, ')', PLAIN, s, s2);
+			atom = parse(v, ')', type, s, s2);
 			assert(SEE(')') || ISERR());
 			NEXT();
 			NOERR();
diff --git a/src/test/regress/expected/regex.out b/src/test/regress/expected/regex.out
index be151858a38..ba2923982f5 100644
--- a/src/test/regress/expected/regex.out
+++ b/src/test/regress/expected/regex.out
@@ -321,3 +321,8 @@ select 'a' ~ '()+\1';
  t
 (1 row)
 
+-- Error conditions
+select 'xyz' ~ 'x(\w)(?=\1)';  -- no backrefs in LACONs
+ERROR:  invalid regular expression: invalid backreference number
+select 'xyz' ~ 'x(\w)(?=(\1))';
+ERROR:  invalid regular expression: invalid backreference number
diff --git a/src/test/regress/sql/regex.sql b/src/test/regress/sql/regex.sql
index c59fa35f24d..7cf5e599822 100644
--- a/src/test/regress/sql/regex.sql
+++ b/src/test/regress/sql/regex.sql
@@ -82,3 +82,7 @@ select 'a' ~ '$()|^\1';
 select 'a' ~ '.. ()|\1';
 select 'a' ~ '()*\1';
 select 'a' ~ '()+\1';
+
+-- Error conditions
+select 'xyz' ~ 'x(\w)(?=\1)';  -- no backrefs in LACONs
+select 'xyz' ~ 'x(\w)(?=(\1))';