diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index b2f60c3d632..74b56ecd070 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -555,9 +555,8 @@ static ObjectAddress ATExecDropColumn(List **wqueue, Relation rel, const char *c
 									  bool recurse, bool recursing,
 									  bool missing_ok, LOCKMODE lockmode,
 									  ObjectAddresses *addrs);
-static void ATPrepAddPrimaryKey(List **wqueue, Relation rel, AlterTableCmd *cmd,
-								bool recurse, LOCKMODE lockmode,
-								AlterTableUtilityContext *context);
+static void ATPrepAddPrimaryKey(AlteredTableInfo *tab, Relation rel,
+								AlterTableCmd *cmd, LOCKMODE lockmode);
 static void verifyNotNullPKCompatible(HeapTuple tuple, const char *colname);
 static ObjectAddress ATExecAddIndex(AlteredTableInfo *tab, Relation rel,
 									IndexStmt *stmt, bool is_rebuild, LOCKMODE lockmode);
@@ -5120,7 +5119,6 @@ ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
 		case AT_AddConstraint:	/* ADD CONSTRAINT */
 			ATSimplePermissions(cmd->subtype, rel,
 								ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_FOREIGN_TABLE);
-			ATPrepAddPrimaryKey(wqueue, rel, cmd, recurse, lockmode, context);
 			if (recurse)
 			{
 				/* recurses at exec time; lock descendants and set flag */
@@ -5368,6 +5366,19 @@ ATRewriteCatalogs(List **wqueue, LOCKMODE lockmode,
 						  lfirst_node(AlterTableCmd, lcmd),
 						  lockmode, pass, context);
 
+			/*
+			 * For ADD PRIMARY KEY without USING INDEX, queue any required NOT
+			 * NULL constraints after transforming all explicit constraints.
+			 * This lets a named NOT NULL constraint take precedence
+			 * regardless of subcommand order. USING INDEX is handled during
+			 * transformation.
+			 */
+			if (pass == AT_PASS_ADD_CONSTR)
+			{
+				foreach_node(AlterTableCmd, cmd, subcmds)
+					ATPrepAddPrimaryKey(tab, tab->rel, cmd, lockmode);
+			}
+
 			/*
 			 * After the ALTER TYPE or SET EXPRESSION pass, do cleanup work
 			 * (this is not done in ATExecAlterColumnType since it should be
@@ -9510,7 +9521,7 @@ ATExecDropColumn(List **wqueue, Relation rel, const char *colName,
  * hierarchy (failing to ensure that leads to funny corner cases).  For the
  * normal case where we're asked to recurse, this routine checks if the
  * not-null constraints exist already, and if not queues a requirement for
- * them to be created by phase 2.
+ * them to be created in the AT_PASS_COL_ATTRS pass.
  *
  * For the case where we're asked not to recurse, we verify that a not-null
  * constraint exists on each column of each (direct) child table, throwing an
@@ -9525,16 +9536,17 @@ ATExecDropColumn(List **wqueue, Relation rel, const char *colName,
  * deadlocks during parallel pg_restore of PKs on partitioned tables.
  */
 static void
-ATPrepAddPrimaryKey(List **wqueue, Relation rel, AlterTableCmd *cmd,
-					bool recurse, LOCKMODE lockmode,
-					AlterTableUtilityContext *context)
+ATPrepAddPrimaryKey(AlteredTableInfo *tab, Relation rel, AlterTableCmd *cmd,
+					LOCKMODE lockmode)
 {
 	Constraint *pkconstr;
 	List	   *children = NIL;
 	bool		got_children = false;
 
 	pkconstr = castNode(Constraint, cmd->def);
-	if (pkconstr->contype != CONSTR_PRIMARY)
+
+	/* USING INDEX queues its own NOT NULL constraints during transformation */
+	if (pkconstr->contype != CONSTR_PRIMARY || pkconstr->indexname != NULL)
 		return;
 
 	/* Verify that columns are not-null, or request that they be made so */
@@ -9558,7 +9570,7 @@ ATPrepAddPrimaryKey(List **wqueue, Relation rel, AlterTableCmd *cmd,
 			heap_freetuple(tuple);
 			continue;
 		}
-		else if (!recurse)
+		else if (!cmd->recurse)
 		{
 			/*
 			 * No constraint on this column.  Asked not to recurse, we won't
@@ -9595,7 +9607,8 @@ ATPrepAddPrimaryKey(List **wqueue, Relation rel, AlterTableCmd *cmd,
 		newcmd->recurse = true;
 		newcmd->def = (Node *) nnconstr;
 
-		ATPrepCmd(wqueue, rel, newcmd, true, false, lockmode, context);
+		tab->subcmds[AT_PASS_COL_ATTRS] =
+			lappend(tab->subcmds[AT_PASS_COL_ATTRS], newcmd);
 	}
 }
 
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index b891d68d4a7..96aa9b8e5fb 100644
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -1046,6 +1046,31 @@ ERROR:  column "test2" of relation "atacc1" contains null values
 -- now add a primary key column with a default (succeeds).
 alter table atacc1 add column test2 int default 0 primary key;
 drop table atacc1;
+-- Replacing a NOT NULL column must create a new constraint for the primary key.
+create table atacc1 (id int not null);
+alter table atacc1 drop column id, add column id int, add primary key (id);
+drop table atacc1;
+-- A NOT NULL constraint dropped in the same ALTER TABLE must be replaced.
+create table atacc1 (id int not null);
+alter table atacc1 alter column id drop not null, add primary key (id);
+drop table atacc1;
+create table atacc1 (id int constraint atacc1_id_nn not null);
+alter table atacc1 drop constraint atacc1_id_nn, add primary key (id);
+drop table atacc1;
+-- ADD PRIMARY KEY must prefer an explicitly named replacement NOT NULL.
+create table atacc1 (id int not null);
+alter table atacc1 alter column id drop not null,
+  add primary key (id), add constraint atacc1_id_nn not null id;
+drop table atacc1;
+create table atacc1 (id int not null);
+alter table atacc1 alter column id drop not null,
+  add constraint atacc1_id_nn not null id, add primary key (id);
+drop table atacc1;
+-- The replacement NOT NULL constraint must propagate to the partitions too.
+create table atacc1 (id int not null) partition by range (id);
+create table atacc1_1 partition of atacc1 for values from (0) to (10);
+alter table atacc1 alter column id drop not null, add primary key (id);
+drop table atacc1;
 -- this combination used to have order-of-execution problems (bug #15580)
 create table atacc1 (a int);
 insert into atacc1 values(1);
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index 9f6c2a4bb08..18f3fdac57a 100644
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -782,6 +782,32 @@ alter table atacc1 add column test2 int primary key;
 alter table atacc1 add column test2 int default 0 primary key;
 drop table atacc1;
 
+-- Replacing a NOT NULL column must create a new constraint for the primary key.
+create table atacc1 (id int not null);
+alter table atacc1 drop column id, add column id int, add primary key (id);
+drop table atacc1;
+-- A NOT NULL constraint dropped in the same ALTER TABLE must be replaced.
+create table atacc1 (id int not null);
+alter table atacc1 alter column id drop not null, add primary key (id);
+drop table atacc1;
+create table atacc1 (id int constraint atacc1_id_nn not null);
+alter table atacc1 drop constraint atacc1_id_nn, add primary key (id);
+drop table atacc1;
+-- ADD PRIMARY KEY must prefer an explicitly named replacement NOT NULL.
+create table atacc1 (id int not null);
+alter table atacc1 alter column id drop not null,
+  add primary key (id), add constraint atacc1_id_nn not null id;
+drop table atacc1;
+create table atacc1 (id int not null);
+alter table atacc1 alter column id drop not null,
+  add constraint atacc1_id_nn not null id, add primary key (id);
+drop table atacc1;
+-- The replacement NOT NULL constraint must propagate to the partitions too.
+create table atacc1 (id int not null) partition by range (id);
+create table atacc1_1 partition of atacc1 for values from (0) to (10);
+alter table atacc1 alter column id drop not null, add primary key (id);
+drop table atacc1;
+
 -- this combination used to have order-of-execution problems (bug #15580)
 create table atacc1 (a int);
 insert into atacc1 values(1);