diff --git a/demo/webcam_demo.py b/demo/webcam_demo.py
index bff300121d..e3801a38d3 100644
--- a/demo/webcam_demo.py
+++ b/demo/webcam_demo.py
@@ -168,6 +168,9 @@ def process_mmdet_results(mmdet_results, class_names=None, cat_ids=1):
     if isinstance(mmdet_results, tuple):
         mmdet_results = mmdet_results[0]
 
+    if isinstance(class_names, str):
+        class_names = (class_names, )
+
     if not isinstance(cat_ids, (list, tuple)):
         cat_ids = [cat_ids]
 
diff --git a/tools/webcam/webcam_apis/nodes/mmdet_node.py b/tools/webcam/webcam_apis/nodes/mmdet_node.py
index 4207647c92..2ff079b3c5 100644
--- a/tools/webcam/webcam_apis/nodes/mmdet_node.py
+++ b/tools/webcam/webcam_apis/nodes/mmdet_node.py
@@ -62,12 +62,16 @@ def _post_process(self, preds):
             dets = preds
             segms = [None] * len(dets)
 
-        assert len(dets) == len(self.model.CLASSES)
-        assert len(segms) == len(self.model.CLASSES)
+        det_model_classes = self.model.CLASSES
+        if isinstance(det_model_classes, str):
+            det_model_classes = (det_model_classes, )
+
+        assert len(dets) == len(det_model_classes)
+        assert len(segms) == len(det_model_classes)
         result = {'preds': [], 'model_cfg': self.model.cfg.copy()}
 
         for i, (cls_name, bboxes,
-                masks) in enumerate(zip(self.model.CLASSES, dets, segms)):
+                masks) in enumerate(zip(det_model_classes, dets, segms)):
             if masks is None:
                 masks = [None] * len(bboxes)
             else: