diff --git a/CRM/Contact/BAO/GroupContactCache.php b/CRM/Contact/BAO/GroupContactCache.php
index 417963ee7fd0..bd5e4a30fa30 100644
--- a/CRM/Contact/BAO/GroupContactCache.php
+++ b/CRM/Contact/BAO/GroupContactCache.php
@@ -721,12 +721,12 @@ protected static function getApiSQL(array $savedSearch, string $addSelect, strin
     list($idField) = explode(' AS ', $apiParams['select'][0]);
     $apiParams['select'] = [
       $addSelect,
-      $idField . ' AS smart_group_contact_id',
+      $idField,
     ];
     $api = \Civi\API\Request::create($savedSearch['api_entity'], 'get', $apiParams);
     $query = new \Civi\Api4\Query\Api4SelectQuery($api);
     $query->forceSelectId = FALSE;
-    $query->getQuery()->having('smart_group_contact_id ' . $excludeClause);
+    $query->getQuery()->having("$idField $excludeClause");
     return $query->getSql();
   }
 
diff --git a/Civi/Api4/Query/Api4SelectQuery.php b/Civi/Api4/Query/Api4SelectQuery.php
index 21298de2a0e4..5bc18313b5c6 100644
--- a/Civi/Api4/Query/Api4SelectQuery.php
+++ b/Civi/Api4/Query/Api4SelectQuery.php
@@ -197,6 +197,9 @@ protected function buildSelectClause() {
       }
       if ($valid) {
         $alias = $expr->getAlias();
+        if ($alias != $expr->getExpr() && isset($this->apiFieldSpec[$alias])) {
+          throw new \API_Exception('Cannot use existing field name as alias');
+        }
         $this->selectAliases[$alias] = $expr->getExpr();
         $this->query->select($expr->render($this->apiFieldSpec) . " AS `$alias`");
       }
diff --git a/Civi/Api4/Query/SqlField.php b/Civi/Api4/Query/SqlField.php
index 712bd7b8cc69..67f1c206a6ff 100644
--- a/Civi/Api4/Query/SqlField.php
+++ b/Civi/Api4/Query/SqlField.php
@@ -17,6 +17,9 @@
 class SqlField extends SqlExpression {
 
   protected function initialize() {
+    if ($this->alias && $this->alias !== $this->expr) {
+      throw new \API_Exception("Aliasing field names is not allowed, only expressions can have an alias.");
+    }
     $this->fields[] = $this->expr;
   }
 
diff --git a/tests/phpunit/api/v4/Action/SqlExpressionTest.php b/tests/phpunit/api/v4/Action/SqlExpressionTest.php
index 3145c9d65657..f99242e03e47 100644
--- a/tests/phpunit/api/v4/Action/SqlExpressionTest.php
+++ b/tests/phpunit/api/v4/Action/SqlExpressionTest.php
@@ -31,7 +31,7 @@ class SqlExpressionTest extends UnitTestCase {
   public function testSelectNull() {
     Contact::create()->addValue('first_name', 'bob')->setCheckPermissions(FALSE)->execute();
     $result = Contact::get()
-      ->addSelect('NULL AS nothing', 'NULL', 'NULL AS b*d char', 'first_name AS firsty')
+      ->addSelect('NULL AS nothing', 'NULL', 'NULL AS b*d char', 'first_name')
       ->addWhere('first_name', '=', 'bob')
       ->setLimit(1)
       ->execute()
@@ -39,7 +39,7 @@ public function testSelectNull() {
     $this->assertNull($result['nothing']);
     $this->assertNull($result['NULL']);
     $this->assertNull($result['b_d_char']);
-    $this->assertEquals('bob', $result['firsty']);
+    $this->assertEquals('bob', $result['first_name']);
     $this->assertArrayNotHasKey('b*d char', $result);
   }
 
@@ -60,16 +60,40 @@ public function testSelectNumbers() {
   public function testSelectStrings() {
     Contact::create()->addValue('first_name', 'bob')->setCheckPermissions(FALSE)->execute();
     $result = Contact::get()
-      ->addSelect('first_name AS bob')
+      ->addSelect('first_name')
       ->addSelect('"hello world" AS hi')
       ->addSelect('"can\'t \"quote\"" AS quot')
       ->addWhere('first_name', '=', 'bob')
       ->setLimit(1)
       ->execute()
       ->first();
-    $this->assertEquals('bob', $result['bob']);
+    $this->assertEquals('bob', $result['first_name']);
     $this->assertEquals('hello world', $result['hi']);
     $this->assertEquals('can\'t "quote"', $result['quot']);
   }
 
+  public function testSelectAlias() {
+    try {
+      Contact::get()
+        ->addSelect('first_name AS bob')
+        ->execute();
+    }
+    catch (\API_Exception $e) {
+      $msg = $e->getMessage();
+    }
+    $this->assertContains('alias', $msg);
+    try {
+      Contact::get()
+        ->addSelect('55 AS sort_name')
+        ->execute();
+    }
+    catch (\API_Exception $e) {
+      $msg = $e->getMessage();
+    }
+    $this->assertContains('existing field name', $msg);
+    Contact::get()
+      ->addSelect('55 AS ok_alias')
+      ->execute();
+  }
+
 }