diff --git a/src/backend/optimizer/plan/analyzejoins.c b/src/backend/optimizer/plan/analyzejoins.c
index c053e32e54d..fb01fbe357a 100644
--- a/src/backend/optimizer/plan/analyzejoins.c
+++ b/src/backend/optimizer/plan/analyzejoins.c
@@ -1657,6 +1657,28 @@ update_eclasses(EquivalenceClass *ec, int from, int to)
 	ec->ec_relids = replace_relid(ec->ec_relids, from, to);
 }
 
+/*
+ * "Logically" compares two RestrictInfo's ignoring the 'rinfo_serial' field,
+ * which makes almost every RestrictInfo unique.  This type of comparison is
+ * useful when removing duplicates while moving RestrictInfo's from removed
+ * relation to remaining relation during self-join elimination.
+ *
+ * XXX: In the future, we might remove the 'rinfo_serial' field completely and
+ * get rid of this function.
+ */
+static bool
+restrict_infos_logically_equal(RestrictInfo *a, RestrictInfo *b)
+{
+	int			saved_rinfo_serial = a->rinfo_serial;
+	bool		result;
+
+	a->rinfo_serial = b->rinfo_serial;
+	result = equal(a, b);
+	a->rinfo_serial = saved_rinfo_serial;
+
+	return result;
+}
+
 /*
  * Remove a relation after we have proven that it participates only in an
  * unneeded unique self join.
@@ -1760,7 +1782,7 @@ remove_self_join_rel(PlannerInfo *root, PlanRowMark *kmark, PlanRowMark *rmark,
 			if (src == rinfo ||
 				(rinfo->parent_ec != NULL
 				 && src->parent_ec == rinfo->parent_ec)
-				|| equal(rinfo->clause, src->clause))
+				|| restrict_infos_logically_equal(rinfo, src))
 			{
 				is_redundant = true;
 				break;
@@ -1788,7 +1810,7 @@ remove_self_join_rel(PlannerInfo *root, PlanRowMark *kmark, PlanRowMark *rmark,
 			if (src == rinfo ||
 				(rinfo->parent_ec != NULL
 				 && src->parent_ec == rinfo->parent_ec)
-				|| equal(rinfo->clause, src->clause))
+				|| restrict_infos_logically_equal(rinfo, src))
 			{
 				is_redundant = true;
 				break;
diff --git a/src/test/regress/expected/join.out b/src/test/regress/expected/join.out
index ffc60eb21d0..063396ab522 100644
--- a/src/test/regress/expected/join.out
+++ b/src/test/regress/expected/join.out
@@ -6742,7 +6742,7 @@ explain (costs off) select 1 from
 reset join_collapse_limit;
 reset enable_seqscan;
 -- Check that clauses from the join filter list is not lost on the self-join removal
-CREATE TABLE emp1 ( id SERIAL PRIMARY KEY NOT NULL, code int);
+CREATE TABLE emp1 (id SERIAL PRIMARY KEY NOT NULL, code int);
 explain (verbose, costs off)
 SELECT * FROM emp1 e1, emp1 e2 WHERE e1.id = e2.id AND e2.code <> e1.code;
                         QUERY PLAN                        
@@ -6880,6 +6880,30 @@ WHERE t1.id = emp1.id RETURNING emp1.id, emp1.code;
          Filter: (id IS NOT NULL)
 (3 rows)
 
+-- Check that SJE does not mistakenly omit qual clauses (bug #18187)
+explain (costs off)
+select 1 from emp1 full join
+    (select * from emp1 t1 join
+        emp1 t2 join emp1 t3 on t2.id = t3.id
+        on true
+    where false) s on true
+where false;
+        QUERY PLAN        
+--------------------------
+ Result
+   One-Time Filter: false
+(2 rows)
+
+select 1 from emp1 full join
+    (select * from emp1 t1 join
+        emp1 t2 join emp1 t3 on t2.id = t3.id
+        on true
+    where false) s on true
+where false;
+ ?column? 
+----------
+(0 rows)
+
 -- We can remove the join even if we find the join can't duplicate rows and
 -- the base quals of each side are different.  In the following case we end up
 -- moving quals over to s1 to make it so it can't match any rows.
diff --git a/src/test/regress/sql/join.sql b/src/test/regress/sql/join.sql
index f51f39eee79..5c420a7c6d6 100644
--- a/src/test/regress/sql/join.sql
+++ b/src/test/regress/sql/join.sql
@@ -2568,7 +2568,7 @@ reset join_collapse_limit;
 reset enable_seqscan;
 
 -- Check that clauses from the join filter list is not lost on the self-join removal
-CREATE TABLE emp1 ( id SERIAL PRIMARY KEY NOT NULL, code int);
+CREATE TABLE emp1 (id SERIAL PRIMARY KEY NOT NULL, code int);
 explain (verbose, costs off)
 SELECT * FROM emp1 e1, emp1 e2 WHERE e1.id = e2.id AND e2.code <> e1.code;
 
@@ -2622,6 +2622,21 @@ WITH t1 AS (SELECT * FROM emp1)
 UPDATE emp1 SET code = t1.code + 1 FROM t1
 WHERE t1.id = emp1.id RETURNING emp1.id, emp1.code;
 
+-- Check that SJE does not mistakenly omit qual clauses (bug #18187)
+explain (costs off)
+select 1 from emp1 full join
+    (select * from emp1 t1 join
+        emp1 t2 join emp1 t3 on t2.id = t3.id
+        on true
+    where false) s on true
+where false;
+select 1 from emp1 full join
+    (select * from emp1 t1 join
+        emp1 t2 join emp1 t3 on t2.id = t3.id
+        on true
+    where false) s on true
+where false;
+
 -- We can remove the join even if we find the join can't duplicate rows and
 -- the base quals of each side are different.  In the following case we end up
 -- moving quals over to s1 to make it so it can't match any rows.