diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index da258968b8c..948c2bf06db 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -3296,12 +3296,19 @@ eval_const_expressions_mutator(Node *node,
 											  fselect->resulttype,
 											  fselect->resulttypmod,
 											  fselect->resultcollid))
-						return (Node *) makeVar(((Var *) arg)->varno,
-												fselect->fieldnum,
-												fselect->resulttype,
-												fselect->resulttypmod,
-												fselect->resultcollid,
-												((Var *) arg)->varlevelsup);
+					{
+						Var		   *newvar;
+
+						newvar = makeVar(((Var *) arg)->varno,
+										 fselect->fieldnum,
+										 fselect->resulttype,
+										 fselect->resulttypmod,
+										 fselect->resultcollid,
+										 ((Var *) arg)->varlevelsup);
+						/* New Var is nullable by same rels as the old one */
+						newvar->varnullingrels = ((Var *) arg)->varnullingrels;
+						return (Node *) newvar;
+					}
 				}
 				if (arg && IsA(arg, RowExpr))
 				{
diff --git a/src/test/regress/expected/join.out b/src/test/regress/expected/join.out
index ddc4e692329..b60f5a67c1e 100644
--- a/src/test/regress/expected/join.out
+++ b/src/test/regress/expected/join.out
@@ -4133,6 +4133,32 @@ select * from mki4(42);
 
 drop function mki8(bigint, bigint);
 drop function mki4(int);
+-- test const-folding of a whole-row Var into a per-field Var
+-- (need to inline a function to reach this case, else parser does it)
+create function f_field_select(t onek) returns int4 as
+$$ select t.unique2; $$ language sql immutable;
+explain (verbose, costs off)
+select (t2.*).unique1, f_field_select(t2) from tenk1 t1
+    left join onek t2 on t1.unique1 = t2.unique1
+    left join int8_tbl t3 on true;
+                             QUERY PLAN                             
+--------------------------------------------------------------------
+ Nested Loop Left Join
+   Output: t2.unique1, t2.unique2
+   ->  Hash Left Join
+         Output: t2.unique1, t2.unique2
+         Hash Cond: (t1.unique1 = t2.unique1)
+         ->  Index Only Scan using tenk1_unique1 on public.tenk1 t1
+               Output: t1.unique1
+         ->  Hash
+               Output: t2.unique1, t2.unique2
+               ->  Seq Scan on public.onek t2
+                     Output: t2.unique1, t2.unique2
+   ->  Materialize
+         ->  Seq Scan on public.int8_tbl t3
+(13 rows)
+
+drop function f_field_select(t onek);
 --
 -- test extraction of restriction OR clauses from join OR clause
 -- (we used to only do this for indexable clauses)
diff --git a/src/test/regress/sql/join.sql b/src/test/regress/sql/join.sql
index a41787d1f1e..fbaee480d32 100644
--- a/src/test/regress/sql/join.sql
+++ b/src/test/regress/sql/join.sql
@@ -1381,6 +1381,18 @@ select * from mki4(42);
 drop function mki8(bigint, bigint);
 drop function mki4(int);
 
+-- test const-folding of a whole-row Var into a per-field Var
+-- (need to inline a function to reach this case, else parser does it)
+create function f_field_select(t onek) returns int4 as
+$$ select t.unique2; $$ language sql immutable;
+
+explain (verbose, costs off)
+select (t2.*).unique1, f_field_select(t2) from tenk1 t1
+    left join onek t2 on t1.unique1 = t2.unique1
+    left join int8_tbl t3 on true;
+
+drop function f_field_select(t onek);
+
 --
 -- test extraction of restriction OR clauses from join OR clause
 -- (we used to only do this for indexable clauses)