Treatment of loss in S-corp - negative cash flow

In 2017 my S-corp lost a great deal of money because of extremely low sales.  This was a temporary condition and I expect a banner year for 2018.  I have never run a loss in the 25 or so years I've been an S corp.  Usually I take excess profits as a dividend, and make a General Journal entry to net those dividends against Retained Earnings.  In 2017 I paid into the corporation and did not take any salary.  Do I show negative Retained Earnings this year, or must I formally make this a loan to the corporation?