diff --git a/core/modules/migrate/src/Plugin/migrate/id_map/Sql.php b/core/modules/migrate/src/Plugin/migrate/id_map/Sql.php
index 37c1c32b57..24ff8c702b 100644
--- a/core/modules/migrate/src/Plugin/migrate/id_map/Sql.php
+++ b/core/modules/migrate/src/Plugin/migrate/id_map/Sql.php
@@ -441,6 +441,9 @@ protected function ensureTables() {
           'description' => 'Messages generated during a migration process',
           'fields' => $fields,
           'primary key' => ['msgid'],
+          'unique keys' => [
+            $this::SOURCE_IDS_HASH => [$this::SOURCE_IDS_HASH],
+          ],
         ];
         $this->getDatabase()->schema()->createTable($this->messageTableName(), $schema);
       }
diff --git a/core/modules/migrate/tests/src/Unit/MigrateSqlIdMapEnsureTablesTest.php b/core/modules/migrate/tests/src/Unit/MigrateSqlIdMapEnsureTablesTest.php
index 826087933c..41db4fb299 100644
--- a/core/modules/migrate/tests/src/Unit/MigrateSqlIdMapEnsureTablesTest.php
+++ b/core/modules/migrate/tests/src/Unit/MigrateSqlIdMapEnsureTablesTest.php
@@ -109,6 +109,9 @@ public function testEnsureTablesNotExist() {
       'description' => 'Messages generated during a migration process',
       'fields' => $fields,
       'primary key' => ['msgid'],
+      'unique keys' => [
+        'source_ids_hash' => ['source_ids_hash'],
+      ],
     ];
 
     $schema = $this->getMockBuilder('Drupal\Core\Database\Schema')