diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index feef999863..1b7e11b93e 100644
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -1126,8 +1126,13 @@ get_constraint_name(Oid conoid)
  *		Given the OID of a unique, primary-key, or exclusion constraint,
  *		return the OID of the underlying index.
  *
- * Return InvalidOid if the index couldn't be found; this suggests the
- * given OID is bogus, but we leave it to caller to decide what to do.
+ * Returns InvalidOid if the constraint could not be found or is of
+ * the wrong type.
+ *
+ * The intent of this function is to return the index "owned" by the
+ * specified constraint.  Therefore we must check contype, since some
+ * pg_constraint entries (e.g. for foreign-key constraints) store the
+ * OID of an index that is referenced but not owned by the constraint.
  */
 Oid
 get_constraint_index(Oid conoid)
@@ -1140,7 +1145,12 @@ get_constraint_index(Oid conoid)
 		Form_pg_constraint contup = (Form_pg_constraint) GETSTRUCT(tp);
 		Oid			result;
 
-		result = contup->conindid;
+		if (contup->contype == CONSTRAINT_UNIQUE ||
+			contup->contype == CONSTRAINT_PRIMARY ||
+			contup->contype == CONSTRAINT_EXCLUSION)
+			result = contup->conindid;
+		else
+			result = InvalidOid;
 		ReleaseSysCache(tp);
 		return result;
 	}
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index 16e0475663..aabc564e2c 100644
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -4502,6 +4502,20 @@ create trigger xtrig
 update bar1 set a = a + 1;
 INFO:  a=1, b=1
 /* End test case for bug #16242 */
+/* Test case for bug #17409 */
+create table attbl (p1 int constraint pk_attbl primary key);
+create table atref (c1 int references attbl(p1));
+cluster attbl using pk_attbl;
+alter table attbl alter column p1 set data type bigint;
+alter table atref alter column c1 set data type bigint;
+drop table attbl, atref;
+create table attbl (p1 int constraint pk_attbl primary key);
+alter table attbl replica identity using index pk_attbl;
+create table atref (c1 int references attbl(p1));
+alter table attbl alter column p1 set data type bigint;
+alter table atref alter column c1 set data type bigint;
+drop table attbl, atref;
+/* End test case for bug #17409 */
 -- Test that ALTER TABLE rewrite preserves a clustered index
 -- for normal indexes and indexes on constraints.
 create table alttype_cluster (a int);
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index ac894c0602..cce1cb1dd3 100644
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -2958,6 +2958,24 @@ update bar1 set a = a + 1;
 
 /* End test case for bug #16242 */
 
+/* Test case for bug #17409 */
+
+create table attbl (p1 int constraint pk_attbl primary key);
+create table atref (c1 int references attbl(p1));
+cluster attbl using pk_attbl;
+alter table attbl alter column p1 set data type bigint;
+alter table atref alter column c1 set data type bigint;
+drop table attbl, atref;
+
+create table attbl (p1 int constraint pk_attbl primary key);
+alter table attbl replica identity using index pk_attbl;
+create table atref (c1 int references attbl(p1));
+alter table attbl alter column p1 set data type bigint;
+alter table atref alter column c1 set data type bigint;
+drop table attbl, atref;
+
+/* End test case for bug #17409 */
+
 -- Test that ALTER TABLE rewrite preserves a clustered index
 -- for normal indexes and indexes on constraints.
 create table alttype_cluster (a int);