diff --git a/inc/_core/model/db/_upgrade.funcs.php b/inc/_core/model/db/_upgrade.funcs.php
index fdbe98f0be..afebc182da 100644
--- a/inc/_core/model/db/_upgrade.funcs.php
+++ b/inc/_core/model/db/_upgrade.funcs.php
@@ -702,7 +702,7 @@ function db_delta( $queries, $exclude_types = array(), $execute = false )
 				{
 					if( ! empty( $primary_key_fields ) )
 					{
-						$column_definition .= ', DROP PRIMARY KEY';
+						$column_definition .= ', DROP PRIMARY KEY, ADD PRIMARY KEY('.$tablefield->Field.')';
 						unset( $obsolete_indices['PRIMARY'] );
 					}
 				}
@@ -1828,4 +1828,4 @@ function db_upgrade_to_utf8_ascii( $show_title = true )
 
 	echo '<p>'.T_('Upgrading done!').'</p>';
 }
-?>
\ No newline at end of file
+?>