diff --git a/contrib/intarray/expected/_int.out b/contrib/intarray/expected/_int.out
index 64d88787632..f2b2b09403c 100644
--- a/contrib/intarray/expected/_int.out
+++ b/contrib/intarray/expected/_int.out
@@ -398,6 +398,21 @@ SELECT '1&(2&(4&(5|!6)))'::query_int;
  1 & 2 & 4 & ( 5 | !6 )
 (1 row)
 
+-- Test for overflow of the int16 "left" field in findoprnd().
+-- This query uses a balanced binary tree to avoid using too much stack.
+DO $$
+DECLARE
+  e text := '1';
+BEGIN
+  FOR i IN 1..15 LOOP
+    e := '(' || e || '&' || e || ')';
+  END LOOP;
+  PERFORM ('0|' || e)::query_int;
+END;
+$$;
+ERROR:  query_int expression is too complex
+CONTEXT:  SQL statement "SELECT ('0|' || e)::query_int"
+PL/pgSQL function inline_code_block line 8 at PERFORM
 CREATE TABLE test__int( a int[] );
 \copy test__int from 'data/test__int.data'
 ANALYZE test__int;
diff --git a/contrib/intarray/sql/_int.sql b/contrib/intarray/sql/_int.sql
index ba4c298151a..f4871d0a7aa 100644
--- a/contrib/intarray/sql/_int.sql
+++ b/contrib/intarray/sql/_int.sql
@@ -75,6 +75,18 @@ SELECT '1&2&4&5&6'::query_int;
 SELECT '1&(2&(4&(5|6)))'::query_int;
 SELECT '1&(2&(4&(5|!6)))'::query_int;
 
+-- Test for overflow of the int16 "left" field in findoprnd().
+-- This query uses a balanced binary tree to avoid using too much stack.
+DO $$
+DECLARE
+  e text := '1';
+BEGIN
+  FOR i IN 1..15 LOOP
+    e := '(' || e || '&' || e || ')';
+  END LOOP;
+  PERFORM ('0|' || e)::query_int;
+END;
+$$;
 
 CREATE TABLE test__int( a int[] );
 \copy test__int from 'data/test__int.data'
diff --git a/contrib/ltree/expected/ltree.out b/contrib/ltree/expected/ltree.out
index 28c321a4cf1..20f6ad7d0fe 100644
--- a/contrib/ltree/expected/ltree.out
+++ b/contrib/ltree/expected/ltree.out
@@ -1267,6 +1267,21 @@ SELECT 'tree.awdfg_qwerty'::ltree @ 'tree & aw_rw%*'::ltxtquery;
  f
 (1 row)
 
+-- Test for overflow of the int16 "left" field in findoprnd().
+-- This query uses a balanced binary tree to avoid using too much stack.
+DO $$
+DECLARE
+  e text := 'a';
+BEGIN
+  FOR i IN 1..14 LOOP
+    e := '(' || e || '&' || e || ')';
+  END LOOP;
+  PERFORM ('b|' || e)::ltxtquery;
+END;
+$$;
+ERROR:  ltxtquery is too large
+CONTEXT:  SQL statement "SELECT ('b|' || e)::ltxtquery"
+PL/pgSQL function inline_code_block line 8 at PERFORM
 --arrays
 SELECT '{1.2.3}'::ltree[] @> '1.2.3.4';
  ?column? 
@@ -8089,3 +8104,12 @@ SELECT count(*) FROM _ltreetest WHERE t ? '{23.*.1,23.*.2}' ;
     15
 (1 row)
 
+-- Test for overflow of lquery_level.totallen.
+SELECT (repeat('x', 255) || repeat('|' || repeat('x', 255), 256))::lquery;
+ERROR:  lquery level is too large
+DETAIL:  Total size of level exceeds the maximum allowed (65535 bytes).
+--- Test for overflow of lquery_level.numvar, with a set of single-char
+--- variants in one level.
+SELECT (repeat('a|', 65535) || 'a')::lquery;
+ERROR:  lquery level has too many variants
+DETAIL:  Number of variants exceeds the maximum allowed (65535).
diff --git a/contrib/ltree/sql/ltree.sql b/contrib/ltree/sql/ltree.sql
index 2a612e347de..b187b53c52c 100644
--- a/contrib/ltree/sql/ltree.sql
+++ b/contrib/ltree/sql/ltree.sql
@@ -246,6 +246,19 @@ SELECT 'tree.awdfg'::ltree @ 'tree & aWdfg@'::ltxtquery;
 SELECT 'tree.awdfg_qwerty'::ltree @ 'tree & aw_qw%*'::ltxtquery;
 SELECT 'tree.awdfg_qwerty'::ltree @ 'tree & aw_rw%*'::ltxtquery;
 
+-- Test for overflow of the int16 "left" field in findoprnd().
+-- This query uses a balanced binary tree to avoid using too much stack.
+DO $$
+DECLARE
+  e text := 'a';
+BEGIN
+  FOR i IN 1..14 LOOP
+    e := '(' || e || '&' || e || ')';
+  END LOOP;
+  PERFORM ('b|' || e)::ltxtquery;
+END;
+$$;
+
 --arrays
 
 SELECT '{1.2.3}'::ltree[] @> '1.2.3.4';
@@ -384,3 +397,10 @@ SELECT count(*) FROM _ltreetest WHERE t ~ '23.*{1}.1' ;
 SELECT count(*) FROM _ltreetest WHERE t ~ '23.*.1' ;
 SELECT count(*) FROM _ltreetest WHERE t ~ '23.*.2' ;
 SELECT count(*) FROM _ltreetest WHERE t ? '{23.*.1,23.*.2}' ;
+
+-- Test for overflow of lquery_level.totallen.
+SELECT (repeat('x', 255) || repeat('|' || repeat('x', 255), 256))::lquery;
+
+--- Test for overflow of lquery_level.numvar, with a set of single-char
+--- variants in one level.
+SELECT (repeat('a|', 65535) || 'a')::lquery;