diff --git a/src/backend/optimizer/util/orclauses.c b/src/backend/optimizer/util/orclauses.c
index 9e954d0d35..8fecabbcda 100644
--- a/src/backend/optimizer/util/orclauses.c
+++ b/src/backend/optimizer/util/orclauses.c
@@ -178,6 +178,7 @@ extract_or_clause(RestrictInfo *or_rinfo, RelOptInfo *rel)
 	{
 		Node	   *orarg = (Node *) lfirst(lc);
 		List	   *subclauses = NIL;
+		Node	   *subclause;
 
 		/* OR arguments should be ANDs or sub-RestrictInfos */
 		if (and_clause(orarg))
@@ -226,9 +227,16 @@ extract_or_clause(RestrictInfo *or_rinfo, RelOptInfo *rel)
 
 		/*
 		 * OK, add subclause(s) to the result OR.  If we found more than one,
-		 * we need an AND node.
+		 * we need an AND node.  But if we found only one, and it is itself an
+		 * OR node, add its subclauses to the result instead; this is needed
+		 * to preserve AND/OR flatness (ie, no OR directly underneath OR).
 		 */
-		clauselist = lappend(clauselist, make_ands_explicit(subclauses));
+		subclause = (Node *) make_ands_explicit(subclauses);
+		if (or_clause(subclause))
+			clauselist = list_concat(clauselist,
+								  list_copy(((BoolExpr *) subclause)->args));
+		else
+			clauselist = lappend(clauselist, subclause);
 	}
 
 	/*
diff --git a/src/test/regress/expected/join.out b/src/test/regress/expected/join.out
index c62a63f674..70f630b3eb 100644
--- a/src/test/regress/expected/join.out
+++ b/src/test/regress/expected/join.out
@@ -2827,6 +2827,33 @@ select * from tenk1 a join tenk1 b on
                            Index Cond: (unique2 = 3)
 (12 rows)
 
+explain (costs off)
+select * from tenk1 a join tenk1 b on
+  (a.unique1 = 1 and b.unique1 = 2) or
+  ((a.unique2 = 3 or a.unique2 = 7) and b.hundred = 4);
+                                                      QUERY PLAN                                                      
+----------------------------------------------------------------------------------------------------------------------
+ Nested Loop
+   Join Filter: (((a.unique1 = 1) AND (b.unique1 = 2)) OR (((a.unique2 = 3) OR (a.unique2 = 7)) AND (b.hundred = 4)))
+   ->  Bitmap Heap Scan on tenk1 b
+         Recheck Cond: ((unique1 = 2) OR (hundred = 4))
+         ->  BitmapOr
+               ->  Bitmap Index Scan on tenk1_unique1
+                     Index Cond: (unique1 = 2)
+               ->  Bitmap Index Scan on tenk1_hundred
+                     Index Cond: (hundred = 4)
+   ->  Materialize
+         ->  Bitmap Heap Scan on tenk1 a
+               Recheck Cond: ((unique1 = 1) OR (unique2 = 3) OR (unique2 = 7))
+               ->  BitmapOr
+                     ->  Bitmap Index Scan on tenk1_unique1
+                           Index Cond: (unique1 = 1)
+                     ->  Bitmap Index Scan on tenk1_unique2
+                           Index Cond: (unique2 = 3)
+                     ->  Bitmap Index Scan on tenk1_unique2
+                           Index Cond: (unique2 = 7)
+(19 rows)
+
 --
 -- test placement of movable quals in a parameterized join tree
 --
diff --git a/src/test/regress/sql/join.sql b/src/test/regress/sql/join.sql
index 1031f26b31..dbb5be64ad 100644
--- a/src/test/regress/sql/join.sql
+++ b/src/test/regress/sql/join.sql
@@ -774,6 +774,10 @@ select * from tenk1 a join tenk1 b on
 explain (costs off)
 select * from tenk1 a join tenk1 b on
   (a.unique1 = 1 and b.unique1 = 2) or (a.unique2 = 3 and b.ten = 4);
+explain (costs off)
+select * from tenk1 a join tenk1 b on
+  (a.unique1 = 1 and b.unique1 = 2) or
+  ((a.unique2 = 3 or a.unique2 = 7) and b.hundred = 4);
 
 --
 -- test placement of movable quals in a parameterized join tree