diff --git a/mmdet/core/loss/losses.py b/mmdet/core/loss/losses.py
index 1e32fca5606bd686bcd5c9ddea114971b77bed61..b2082002af82677d464a9e1bdddc9dc57a6129e0 100644
--- a/mmdet/core/loss/losses.py
+++ b/mmdet/core/loss/losses.py
@@ -92,6 +92,8 @@ def accuracy(pred, target, topk=1):
     if isinstance(topk, int):
         topk = (topk, )
         return_single = True
+    else:
+        return_single = False
 
     maxk = max(topk)
     _, pred_label = pred.topk(maxk, 1, True, True)
diff --git a/tools/test.py b/tools/test.py
index d0537b3c64ebc51ddf410d8064278ba1da8eaa37..8aa23ea7ec8d1758fd06df6c47e765026dcd071e 100644
--- a/tools/test.py
+++ b/tools/test.py
@@ -23,7 +23,7 @@ def single_test(model, data_loader, show=False):
 
         if show:
             model.module.show_result(data, result, dataset.img_norm_cfg,
-                                     dataset.CLASSES)
+                                     dataset=dataset.CLASSES)
 
         batch_size = data['img'][0].size(0)
         for _ in range(batch_size):