diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c
index c4fcd0076ea..771781e28ca 100644
--- a/src/backend/utils/adt/selfuncs.c
+++ b/src/backend/utils/adt/selfuncs.c
@@ -120,6 +120,7 @@
 #include "optimizer/plancat.h"
 #include "parser/parse_clause.h"
 #include "parser/parsetree.h"
+#include "rewrite/rewriteManip.h"
 #include "statistics/statistics.h"
 #include "storage/bufmgr.h"
 #include "utils/acl.h"
@@ -3273,6 +3274,15 @@ add_unique_group_var(PlannerInfo *root, List *varinfos,
 
 	ndistinct = get_variable_numdistinct(vardata, &isdefault);
 
+	/*
+	 * The nullingrels bits within the var could cause the same var to be
+	 * counted multiple times if it's marked with different nullingrels.  They
+	 * could also prevent us from matching the var to the expressions in
+	 * extended statistics (see estimate_multivariate_ndistinct).  So strip
+	 * them out first.
+	 */
+	var = remove_nulling_relids(var, root->outer_join_rels, NULL);
+
 	foreach(lc, varinfos)
 	{
 		varinfo = (GroupVarInfo *) lfirst(lc);
@@ -4980,6 +4990,7 @@ examine_variable(PlannerInfo *root, Node *node, int varRelid,
 {
 	Node	   *basenode;
 	Relids		varnos;
+	Relids		basevarnos;
 	RelOptInfo *onerel;
 
 	/* Make sure we don't return dangling pointers in vardata */
@@ -5021,10 +5032,11 @@ examine_variable(PlannerInfo *root, Node *node, int varRelid,
 	 * relation are considered "real" vars.
 	 */
 	varnos = pull_varnos(root, basenode);
+	basevarnos = bms_difference(varnos, root->outer_join_rels);
 
 	onerel = NULL;
 
-	switch (bms_membership(varnos))
+	switch (bms_membership(basevarnos))
 	{
 		case BMS_EMPTY_SET:
 			/* No Vars at all ... must be pseudo-constant clause */
@@ -5033,7 +5045,7 @@ examine_variable(PlannerInfo *root, Node *node, int varRelid,
 			if (varRelid == 0 || bms_is_member(varRelid, varnos))
 			{
 				onerel = find_base_rel(root,
-									   (varRelid ? varRelid : bms_singleton_member(varnos)));
+									   (varRelid ? varRelid : bms_singleton_member(basevarnos)));
 				vardata->rel = onerel;
 				node = basenode;	/* strip any relabeling */
 			}
@@ -5057,7 +5069,7 @@ examine_variable(PlannerInfo *root, Node *node, int varRelid,
 			break;
 	}
 
-	bms_free(varnos);
+	bms_free(basevarnos);
 
 	vardata->var = node;
 	vardata->atttype = exprType(node);
@@ -5082,6 +5094,14 @@ examine_variable(PlannerInfo *root, Node *node, int varRelid,
 		ListCell   *slist;
 		Oid			userid;
 
+		/*
+		 * The nullingrels bits within the expression could prevent us from
+		 * matching it to expressional index columns or to the expressions in
+		 * extended statistics.  So strip them out first.
+		 */
+		if (bms_overlap(varnos, root->outer_join_rels))
+			node = remove_nulling_relids(node, root->outer_join_rels, NULL);
+
 		/*
 		 * Determine the user ID to use for privilege checks: either
 		 * onerel->userid if it's set (e.g., in case we're accessing the table
@@ -5352,6 +5372,8 @@ examine_variable(PlannerInfo *root, Node *node, int varRelid,
 			}
 		}
 	}
+
+	bms_free(varnos);
 }
 
 /*
diff --git a/src/test/regress/expected/join.out b/src/test/regress/expected/join.out
index 9af8d61a732..84e35981ed8 100644
--- a/src/test/regress/expected/join.out
+++ b/src/test/regress/expected/join.out
@@ -2517,10 +2517,11 @@ where t1.f1 = coalesce(t2.f1, 1);
                ->  Materialize
                      ->  Seq Scan on int4_tbl t2
                            Filter: (f1 > 1)
-         ->  Seq Scan on int4_tbl t3
+         ->  Materialize
+               ->  Seq Scan on int4_tbl t3
    ->  Materialize
          ->  Seq Scan on int4_tbl t4
-(13 rows)
+(14 rows)
 
 explain (costs off)
 select * from int4_tbl t1
@@ -7981,3 +7982,24 @@ where exists (select 1 from j3
 (13 rows)
 
 drop table j3;
+-- Test that we do not account for nullingrels when looking up statistics
+CREATE TABLE group_tbl (a INT, b INT);
+INSERT INTO group_tbl SELECT 1, 1;
+CREATE STATISTICS group_tbl_stat (ndistinct) ON a, b FROM group_tbl;
+ANALYZE group_tbl;
+EXPLAIN (COSTS OFF)
+SELECT 1 FROM group_tbl t1
+    LEFT JOIN (SELECT a c1, COALESCE(a) c2 FROM group_tbl t2) s ON TRUE
+GROUP BY s.c1, s.c2;
+                 QUERY PLAN                 
+--------------------------------------------
+ Group
+   Group Key: t2.a, (COALESCE(t2.a))
+   ->  Sort
+         Sort Key: t2.a, (COALESCE(t2.a))
+         ->  Nested Loop Left Join
+               ->  Seq Scan on group_tbl t1
+               ->  Seq Scan on group_tbl t2
+(7 rows)
+
+DROP TABLE group_tbl;
diff --git a/src/test/regress/sql/join.sql b/src/test/regress/sql/join.sql
index 41949d41dd6..d6f646a1d50 100644
--- a/src/test/regress/sql/join.sql
+++ b/src/test/regress/sql/join.sql
@@ -2928,3 +2928,16 @@ where exists (select 1 from j3
       and t1.unique1 < 1;
 
 drop table j3;
+
+-- Test that we do not account for nullingrels when looking up statistics
+CREATE TABLE group_tbl (a INT, b INT);
+INSERT INTO group_tbl SELECT 1, 1;
+CREATE STATISTICS group_tbl_stat (ndistinct) ON a, b FROM group_tbl;
+ANALYZE group_tbl;
+
+EXPLAIN (COSTS OFF)
+SELECT 1 FROM group_tbl t1
+    LEFT JOIN (SELECT a c1, COALESCE(a) c2 FROM group_tbl t2) s ON TRUE
+GROUP BY s.c1, s.c2;
+
+DROP TABLE group_tbl;