diff --git a/wekws/model/mdtc.py b/wekws/model/mdtc.py
index 736eca4..385cd63 100644
--- a/wekws/model/mdtc.py
+++ b/wekws/model/mdtc.py
@@ -13,6 +13,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from typing import Tuple
+
 import torch
 import torch.nn as nn
 import torch.nn.functional as F
@@ -205,7 +207,11 @@ class MDTC(nn.Module):
         self.half_receptive_fields = self.receptive_fields // 2
         print('Receptive Fields: %d' % self.receptive_fields)
 
-    def forward(self, x: torch.Tensor):
+    def forward(
+        self,
+        x: torch.Tensor,
+        in_cache: torch.Tensor = torch.zeros(0, 0, 0, dtype=torch.float)
+    ) -> Tuple[torch.Tensor, torch.Tensor]:
         if self.causal:
             outputs = F.pad(x, (0, 0, self.receptive_fields, 0, 0, 0),
                             'constant')
@@ -241,7 +247,8 @@ class MDTC(nn.Module):
         for x in normalized_outputs:
             outputs += x
         outputs = outputs.transpose(1, 2)
-        return outputs, None
+        # TODO(Binbin Zhang): Fix cache
+        return outputs, in_cache
 
 
 if __name__ == '__main__':