diff --git a/transformers/modeling_encoder_decoder.py b/transformers/modeling_encoder_decoder.py
index 162e2f8b3b..a884abd0a2 100644
--- a/transformers/modeling_encoder_decoder.py
+++ b/transformers/modeling_encoder_decoder.py
@@ -114,23 +114,28 @@ class PreTrainedEncoderDecoder(nn.Module):
         # `encoder_`), decoder-specific (prefixed by `decoder_`) and those
         # that apply to the model as a whole.
         # We let the specific kwargs override the common ones in case of conflict.
-        kwargs_encoder = {
-            argument[len("encoder_"):]: value
-            for argument, value in kwargs.items()
-            if argument.startswith("encoder_")
-        }
-        kwargs_decoder = {
-            argument[len("decoder_"):]: value
-            for argument, value in kwargs.items()
-            if argument.startswith("decoder_")
-        }
         kwargs_common = {
             argument: value
             for argument, value in kwargs.items()
-            if not (argument.startswith("encoder_") or argument.startswith("decoder_"))
+            if not argument.startswith("encoder_")
+            and not argument.startswith("decoder_")
         }
-        kwargs_decoder = dict(kwargs_common, **kwargs_decoder)
-        kwargs_encoder = dict(kwargs_common, **kwargs_encoder)
+        kwargs_decoder = kwargs_common.copy()
+        kwargs_encoder = kwargs_common.copy()
+        kwargs_encoder.update(
+            {
+                argument[len("encoder_") :]: value
+                for argument, value in kwargs.items()
+                if argument.startswith("encoder_")
+            }
+        )
+        kwargs_decoder.update(
+            {
+                argument[len("decoder_") :]: value
+                for argument, value in kwargs.items()
+                if argument.startswith("decoder_")
+            }
+        )
 
         # Load and initialize the encoder and decoder
         # The distinction between encoder and decoder at the model level is made
@@ -185,35 +190,44 @@ class PreTrainedEncoderDecoder(nn.Module):
         # `encoder_`), decoder-specific (prefixed by `decoder_`) and those
         # that apply to the model as whole.
         # We let the specific kwargs override the common ones in case of conflict.
-        kwargs_encoder = {
-            argument[len("encoder_"):]: value
-            for argument, value in kwargs.items()
-            if argument.startswith("encoder_")
-        }
-        kwargs_decoder = {
-            argument[len("decoder_"):]: value
-            for argument, value in kwargs.items()
-            if argument.startswith("decoder_")
-        }
         kwargs_common = {
             argument: value
             for argument, value in kwargs.items()
-            if not (argument.startswith("encoder_") or argument.startswith("decoder_"))
+            if not argument.startswith("encoder_")
+            and not argument.startswith("decoder_")
         }
-        kwargs_decoder = dict(kwargs_common, **kwargs_decoder)
-        kwargs_encoder = dict(kwargs_common, **kwargs_encoder)
+        kwargs_decoder = kwargs_common.copy()
+        kwargs_encoder = kwargs_common.copy()
+        kwargs_encoder.update(
+            {
+                argument[len("encoder_") :]: value
+                for argument, value in kwargs.items()
+                if argument.startswith("encoder_")
+            }
+        )
+        kwargs_decoder.update(
+            {
+                argument[len("decoder_") :]: value
+                for argument, value in kwargs.items()
+                if argument.startswith("decoder_")
+            }
+        )
 
         # Encode if needed (training, first prediction pass)
         encoder_hidden_states = kwargs_encoder.pop("hidden_states", None)
         if encoder_hidden_states is None:
             encoder_outputs = self.encoder(encoder_input_ids, **kwargs_encoder)
-            encoder_hidden_states = encoder_outputs[0]  # output the last layer hidden state
+            encoder_hidden_states = encoder_outputs[
+                0
+            ]  # output the last layer hidden state
         else:
             encoder_outputs = ()
 
         # Decode
         kwargs_decoder["encoder_hidden_states"] = encoder_hidden_states
-        kwargs_decoder["encoder_attention_mask"] = kwargs_encoder.get("attention_mask", None)
+        kwargs_decoder["encoder_attention_mask"] = kwargs_encoder.get(
+            "attention_mask", None
+        )
         decoder_outputs = self.decoder(decoder_input_ids, **kwargs_decoder)
 
         return decoder_outputs + encoder_outputs
@@ -235,6 +249,7 @@ class Model2Model(PreTrainedEncoderDecoder):
             decoder = BertForMaskedLM(config)
             model = Model2Model.from_pretrained('bert-base-uncased', decoder_model=decoder)
     """
+
     def __init__(self, *args, **kwargs):
         super(Model2Model, self).__init__(*args, **kwargs)
         self.tie_weights()