diff --git a/egs/librispeech/ASR/transducer/rnn.py b/egs/librispeech/ASR/transducer/rnn.py
index 062a27645..92ef17dcc 100644
--- a/egs/librispeech/ASR/transducer/rnn.py
+++ b/egs/librispeech/ASR/transducer/rnn.py
@@ -23,11 +23,12 @@ as a reference.
 """
 
 import math
-from typing import List, Optional, Tuple
+from typing import List, Optional, Tuple, Type
 
 import torch
 import torch.nn as nn
 import torch.nn.functional as F
+from typeguard import check_argument_types
 
 
 class LayerNormLSTMCell(nn.Module):
@@ -58,7 +59,7 @@ class LayerNormLSTMCell(nn.Module):
         input_size: int,
         hidden_size: int,
         bias: bool = True,
-        ln: nn.Module = nn.LayerNorm,
+        ln: Type[nn.Module] = nn.LayerNorm,
         proj_size: int = 0,
         device=None,
         dtype=None,
@@ -85,6 +86,7 @@ class LayerNormLSTMCell(nn.Module):
             case, the shape of `h` is (batch_size, proj_size).
             See https://arxiv.org/pdf/1402.1128.pdf
         """
+        assert check_argument_types()
         super().__init__()
         factory_kwargs = {"device": device, "dtype": dtype}
         self.input_size = input_size
@@ -163,6 +165,7 @@ class LayerNormLSTMCell(nn.Module):
             - `next_c`: It is of shape (batch_size, hidden_size) containing the
               next cell state for each element in the batch.
         """
+        assert check_argument_types()
         if state is None:
             zeros = torch.zeros(
                 input.size(0),
@@ -233,7 +236,7 @@ class LayerNormLSTMLayer(nn.Module):
         input_size: int,
         hidden_size: int,
         bias: bool = True,
-        ln: nn.Module = nn.LayerNorm,
+        ln: Type[nn.Module] = nn.LayerNorm,
         proj_size: int = 0,
         device=None,
         dtype=None,
@@ -241,6 +244,7 @@ class LayerNormLSTMLayer(nn.Module):
         """
         See the args in LayerNormLSTMCell
         """
+        assert check_argument_types()
         super().__init__()
         self.cell = LayerNormLSTMCell(
             input_size=input_size,
@@ -309,13 +313,14 @@ class LayerNormLSTM(nn.Module):
         num_layers: int,
         bias: bool = True,
         proj_size: int = 0,
-        ln: nn.Module = nn.LayerNorm,
+        ln: Type[nn.Module] = nn.LayerNorm,
         device=None,
         dtype=None,
     ):
         """
         See the args in LayerNormLSTMLayer.
         """
+        assert check_argument_types()
         super().__init__()
         assert num_layers >= 1
         factory_kwargs = dict(
@@ -398,7 +403,7 @@ class LayerNormGRUCell(nn.Module):
         input_size: int,
         hidden_size: int,
         bias: bool = True,
-        ln: nn.Module = nn.LayerNorm,
+        ln: Type[nn.Module] = nn.LayerNorm,
         device=None,
         dtype=None,
     ):
@@ -418,6 +423,7 @@ class LayerNormGRUCell(nn.Module):
             by `ln`. We pass it as an argument so that we can replace it
             with `nn.Identity` at the testing time.
         """
+        assert check_argument_types()
         super().__init__()
         factory_kwargs = {"device": device, "dtype": dtype}
         self.input_size = input_size
@@ -525,13 +531,14 @@ class LayerNormGRULayer(nn.Module):
         input_size: int,
         hidden_size: int,
         bias: bool = True,
-        ln: nn.Module = nn.LayerNorm,
+        ln: Type[nn.Module] = nn.LayerNorm,
         device=None,
         dtype=None,
     ):
         """
         See the args in LayerNormGRUCell
         """
+        assert check_argument_types()
         super().__init__()
         self.cell = LayerNormGRUCell(
             input_size=input_size,
@@ -591,13 +598,14 @@ class LayerNormGRU(nn.Module):
         hidden_size: int,
         num_layers: int,
         bias: bool = True,
-        ln: nn.Module = nn.LayerNorm,
+        ln: Type[nn.Module] = nn.LayerNorm,
         device=None,
         dtype=None,
     ):
         """
         See the args in LayerNormGRULayer.
         """
+        assert check_argument_types()
         super().__init__()
         assert num_layers >= 1
         factory_kwargs = dict(