diff -u b/core/modules/pgsql/src/Driver/Database/pgsql/Connection.php b/core/modules/pgsql/src/Driver/Database/pgsql/Connection.php
--- b/core/modules/pgsql/src/Driver/Database/pgsql/Connection.php
+++ b/core/modules/pgsql/src/Driver/Database/pgsql/Connection.php
@@ -73,6 +73,12 @@
    * Constructs a connection object.
    */
   public function __construct(\PDO $connection, array $connection_options) {
+    // Sanitize the schema name here, so we do not have to do it in other
+    // functions.
+    if (isset($connection_options['schema']) && ($connection_options['schema'] !== 'public')) {
+      $connection_options['schema'] = preg_replace('/[^A-Za-z0-9_]+/', '', $connection_options['schema']);
+    }
+
     // We need to set the connectionOptions before the parent, because setPrefix
     // needs this.
     $this->connectionOptions = $connection_options;
@@ -99,8 +105,7 @@
     // default schema name.
     $quoted_schema = '';
     if (isset($this->connectionOptions['schema']) && ($this->connectionOptions['schema'] !== 'public')) {
-      $sanitizedSchema = preg_replace('/[^A-Za-z0-9_]+/', '', $this->connectionOptions['schema']);
-      $quoted_schema = $this->identifierQuotes[0] . $sanitizedSchema . $this->identifierQuotes[1] . '.';
+      $quoted_schema = $this->identifierQuotes[0] . $this->connectionOptions['schema'] . $this->identifierQuotes[1] . '.';
     }
 
     $this->tablePlaceholderReplacements = [
diff -u b/core/modules/pgsql/src/Driver/Database/pgsql/Schema.php b/core/modules/pgsql/src/Driver/Database/pgsql/Schema.php
--- b/core/modules/pgsql/src/Driver/Database/pgsql/Schema.php
+++ b/core/modules/pgsql/src/Driver/Database/pgsql/Schema.php
@@ -59,7 +59,6 @@
     // If the schema is not set in the connection options then schema defaults
     // to public.
     $this->defaultSchema = $connection->getConnectionOptions()['schema'] ?? 'public';
-    $this->defaultSchema = preg_replace('/[^A-Za-z0-9_]+/', '', $this->defaultSchema);
   }
 
   /**
@@ -134,7 +133,7 @@
     // Take into account that temporary tables are stored in a different schema.
     // \Drupal\Core\Database\Connection::generateTemporaryTableName() sets the
     // 'db_temporary_' prefix to all temporary tables.
-    if (strpos($table, 'db_temporary_') !== FALSE) {
+    if (str_contains($table, 'db_temporary_')) {
       $key = $quoted_key = $this->getTempNamespaceName() . '.' . $prefixed_table;
     }
     else {
@@ -1104,7 +1103,7 @@
   protected function getSequenceName(string $table, string $column): ?string {
     return $this->connection
       ->query("SELECT pg_get_serial_sequence(:table, :column)", [
-        ':table' => $this->connection->getPrefix() . $table,
+        ':table' => $this->defaultSchema . '.' . $this->connection->getPrefix() . $table,
         ':column' => $column,
       ])
       ->fetchField();
diff -u b/core/modules/pgsql/tests/src/Kernel/pgsql/NonPublicSchemaTest.php b/core/modules/pgsql/tests/src/Kernel/pgsql/NonPublicSchemaTest.php
--- b/core/modules/pgsql/tests/src/Kernel/pgsql/NonPublicSchemaTest.php
+++ b/core/modules/pgsql/tests/src/Kernel/pgsql/NonPublicSchemaTest.php
@@ -15,7 +15,6 @@
  *
  * @group Database
  * @coversDefaultClass \Drupal\pgsql\Driver\Database\pgsql\Schema
- * @coversDefaultClass \Drupal\pgsql\Driver\Database\pgsql\Connection
  */
 class NonPublicSchemaTest extends DriverSpecificKernelTestBase {
 
@@ -138,8 +137,8 @@
   }
 
   /**
-   * @covers ::insert
-   * @covers ::select
+   * @covers \Drupal\Core\Database\Connection::insert
+   * @covers \Drupal\Core\Database\Connection::select
    */
   public function testInsert(): void {
     $num_records_before = $this->testingFakeConnection->query('SELECT COUNT(*) FROM {faking_table}')->fetchField();
@@ -162,7 +161,7 @@
   }
 
   /**
-   * @covers ::update
+   * @covers \Drupal\Core\Database\Connection::update
    */
   public function testUpdate(): void {
     $updated_record = $this->testingFakeConnection->update('faking_table')
@@ -178,7 +177,7 @@
   }
 
   /**
-   * @covers ::upsert
+   * @covers \Drupal\Core\Database\Connection::upsert
    */
   public function testUpsert(): void {
     $num_records_before = $this->testingFakeConnection->query('SELECT COUNT(*) FROM {faking_table}')->fetchField();
@@ -217,7 +216,7 @@
   }
 
   /**
-   * @covers ::merge
+   * @covers \Drupal\Core\Database\Connection::merge
    */
   public function testMerge(): void {
     $num_records_before = $this->testingFakeConnection->query('SELECT COUNT(*) FROM {faking_table}')->fetchField();
@@ -238,8 +237,8 @@
   }
 
   /**
-   * @covers ::delete
-   * @covers ::truncate
+   * @covers \Drupal\Core\Database\Connection::delete
+   * @covers \Drupal\Core\Database\Connection::truncate
    */
   public function testDelete(): void {
     $num_records_before = $this->testingFakeConnection->query('SELECT COUNT(*) FROM {faking_table}')->fetchField();