diff --git a/eole/decoders/ensemble.py b/eole/decoders/ensemble.py
index 8a314b655..2eec7cf24 100644
--- a/eole/decoders/ensemble.py
+++ b/eole/decoders/ensemble.py
@@ -92,7 +92,7 @@ def forward(self, emb, enc_out=None, src_len=None, step=None, **kwargs):
                     enc_out=None if enc_out is None else enc_out[i],
                     src_len=src_len,
                     step=step,
-                    **kwargs
+                    **kwargs,
                 )
                 for i, model_decoder in enumerate(self.model_decoders)
             ]
diff --git a/eole/transforms/misc.py b/eole/transforms/misc.py
index c65cab20c..d681df5ba 100644
--- a/eole/transforms/misc.py
+++ b/eole/transforms/misc.py
@@ -146,7 +146,7 @@ def warm_up(self, vocabs=None):
     def _prepend(self, example, prefix):
         """Prepend `prefix` to `tokens`."""
         for side, side_prefix in prefix.items():
-            if example.get(side) is not None:
+            if example.get(side) is not None and len(side_prefix) > 0:
                 example[side] = side_prefix.split(" ") + example[side]
             elif len(side_prefix) > 0:
                 example[side] = side_prefix.split(" ")
@@ -167,7 +167,7 @@ def apply(self, example, is_train=False, stats=None, **kwargs):
 
     def apply_reverse(self, predicted):
         def _removeprefix(s, prefix):
-            if s.startswith(prefix) and len(prefix) > 0:
+            if len(prefix) > 0 and s.startswith(prefix):
                 return s[len(prefix) + 1 :]
             else:
                 return s
@@ -249,7 +249,7 @@ def warm_up(self, vocabs=None):
     def _append(self, example, suffix):
         """Prepend `suffix` to `tokens`."""
         for side, side_suffix in suffix.items():
-            if example.get(side) is not None:
+            if example.get(side) is not None and len(side_suffix) > 0:
                 example[side] = example[side] + side_suffix.split(" ")
             elif len(side_suffix) > 0:
                 example[side] = side_suffix.split(" ")