diff --git a/mmseg/models/decode_heads/knet_head.py b/mmseg/models/decode_heads/knet_head.py
index f73daccb6..78a270277 100644
--- a/mmseg/models/decode_heads/knet_head.py
+++ b/mmseg/models/decode_heads/knet_head.py
@@ -411,6 +411,9 @@ class IterativeDecodeHead(BaseDecodeHead):
 
     def __init__(self, num_stages, kernel_generate_head, kernel_update_head,
                  **kwargs):
+        # ``IterativeDecodeHead`` would skip initialization of
+        # ``BaseDecodeHead`` which would be called when building
+        # ``self.kernel_generate_head``.
         super(BaseDecodeHead, self).__init__(**kwargs)
         assert num_stages == len(kernel_update_head)
         self.num_stages = num_stages
@@ -420,6 +423,7 @@ class IterativeDecodeHead(BaseDecodeHead):
         self.num_classes = self.kernel_generate_head.num_classes
         self.input_transform = self.kernel_generate_head.input_transform
         self.ignore_index = self.kernel_generate_head.ignore_index
+        self.out_channels = self.num_classes
 
         for head_cfg in kernel_update_head:
             self.kernel_update_head.append(build_head(head_cfg))