diff --git a/lib/private/DB/MigrationService.php b/lib/private/DB/MigrationService.php
index 92f45dfdbe83a..13bbe8dc5d049 100644
--- a/lib/private/DB/MigrationService.php
+++ b/lib/private/DB/MigrationService.php
@@ -652,7 +652,10 @@ public function ensureOracleConstraints(Schema $sourceSchema, Schema $targetSche
 				if ($isUsingDefaultName && \strlen($table->getName()) - $prefixLength >= 23) {
 					throw new \InvalidArgumentException('Primary index name on "' . $table->getName() . '" is too long.');
 				}
-				// } elseif (!$primaryKey instanceof Index && !$sourceTable instanceof Table) {
+			} elseif (!$primaryKey instanceof Index && !$sourceTable instanceof Table) {
+				/** @var LoggerInterface $logger */
+				$logger = \OC::$server->get(LoggerInterface::class);
+				$logger->error('Table "' . $table->getName() . '" has no primary key and therefor will not behave sane in clustered setups. This will throw an exception and not be installable in a future version of Nextcloud.');
 				// throw new \InvalidArgumentException('Table "' . $table->getName() . '" has no primary key and therefor will not behave sane in clustered setups.');
 			}
 		}