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
@@ -862,13 +862,7 @@
       return FALSE;
     }
 
-    // Add the schema if not using the default one.
-    $index_name = $this->ensureIdentifiersLength($table, $name, 'idx');
-    // Remove leading and trailing quotes.
-    $index_name = str_replace('"', '', $index_name);
-    $prefix_info = $this->getPrefixInfo($table);
-
-    $this->connection->query('DROP INDEX ' . $this->connection->escapeTable($prefix_info['schema'] . '.' . $index_name));
+    $this->connection->query('DROP INDEX ' . $this->defaultSchema . '.' . $this->ensureIdentifiersLength($table, $name, 'idx'));
     $this->resetTableInformation($table);
     return TRUE;
   }
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
@@ -17,7 +17,6 @@
  */
 class NonPublicSchemaTest extends DriverSpecificKernelTestBase {
 
-
   use DatabaseTestSchemaDataTrait;
   use DatabaseTestSchemaInstallTrait;