diff -r bd5008a7dcbd -r 14fe60a65c69 plugins/mod_storage_sql.lua
--- a/plugins/mod_storage_sql.lua	Mon Jan 23 19:32:07 2017 +0100
+++ b/plugins/mod_storage_sql.lua	Tue Jan 24 19:26:40 2017 +0100
@@ -287,7 +287,7 @@
 function archive_store:delete(username, query)
 	query = query or {};
 	local user,store = username,self.store;
-	local stmt, err = engine:transaction(function()
+	local ok, stmt = engine:transaction(function()
 		local sql_query = "DELETE FROM `prosodyarchive` WHERE %s;";
 		local args = { host, user or "", store, };
 		local where = { "`host` = ?", "`user` = ?", "`store` = ?", };
@@ -300,7 +300,7 @@
 		sql_query = sql_query:format(t_concat(where, " AND "));
 		return engine:delete(sql_query, unpack(args));
 	end);
-	return stmt and stmt:affected() or nil, err;
+	return ok and stmt:affected(), stmt;
 end
 
 local stores = {