diff --git a/src/backend/statistics/dependencies.c b/src/backend/statistics/dependencies.c
index 48d5a53c..d12d5f27 100644
--- a/src/backend/statistics/dependencies.c
+++ b/src/backend/statistics/dependencies.c
@@ -1493,22 +1493,17 @@ dependencies_clauselist_selectivity(PlannerInfo *root,
 		/* make sure the attnum is positive (valid AttrNumber) */
 		attnum = list_attnums[i] + attnum_offset;
 
-		/*
-		 * Either it's a regular attribute, or it's an expression, in which
-		 * case we must not have seen it before (expressions are unique).
-		 *
-		 * XXX Check whether it's a regular attribute has to be done using the
-		 * original attnum, while the second check has to use the value with
-		 * an offset.
-		 */
-		Assert(AttrNumberIsForUserDefinedAttr(list_attnums[i]) ||
-			   !bms_is_member(attnum, clauses_attnums));
-
 		/*
 		 * Remember the offset attnum, both for attributes and expressions.
 		 * We'll pass list_attnums to clauselist_apply_dependencies, which
 		 * uses it to identify clauses in a bitmap. We could also pass the
 		 * offset, but this is more convenient.
+		 *
+		 * Several clauses may share the same attnum, whether it's a regular
+		 * attribute or an expression (a duplicate expression was assigned the
+		 * same attnum above), so the attnum may already be in the bitmap.
+		 * clauselist_apply_dependencies estimates all the clauses for one
+		 * attnum together.
 		 */
 		list_attnums[i] = attnum;
 
diff --git a/src/test/regress/expected/stats_ext.out b/src/test/regress/expected/stats_ext.out
index 4512670d..ac79c1ef 100644
--- a/src/test/regress/expected/stats_ext.out
+++ b/src/test/regress/expected/stats_ext.out
@@ -1763,6 +1763,13 @@ SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies WHERE
          3 |    100
 (1 row)
 
+-- multiple clauses referencing the same expression
+SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies WHERE (a * 2) = 2 AND (a * 2) IN (2, 102) AND upper(b) = ''1''');
+ estimated | actual 
+-----------+--------
+         1 |     50
+(1 row)
+
 -- ANY
 SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies WHERE (a * 2) = ANY (ARRAY[2, 102]) AND upper(b) = ''1''');
  estimated | actual 
diff --git a/src/test/regress/sql/stats_ext.sql b/src/test/regress/sql/stats_ext.sql
index a9176e74..f2a429e6 100644
--- a/src/test/regress/sql/stats_ext.sql
+++ b/src/test/regress/sql/stats_ext.sql
@@ -875,6 +875,9 @@ SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies WHERE
 -- OR clauses referencing different attributes
 SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies WHERE ((a * 2) = 2 OR upper(b) = ''1'') AND upper(b) = ''1''');
 
+-- multiple clauses referencing the same expression
+SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies WHERE (a * 2) = 2 AND (a * 2) IN (2, 102) AND upper(b) = ''1''');
+
 -- ANY
 SELECT * FROM check_estimated_rows('SELECT * FROM functional_dependencies WHERE (a * 2) = ANY (ARRAY[2, 102]) AND upper(b) = ''1''');