diff --git a/tst/transformer.py b/tst/transformer.py
index 1062b13..4d5a070 100644
--- a/tst/transformer.py
+++ b/tst/transformer.py
@@ -47,9 +47,9 @@ class Transformer(nn.Module):
         One of ``'chunk'``, ``'window'`` or ``None``. Default is ``'chunk'``.
     pe:
         Type of positional encoding to add.
-        Must be one of ``'original'``, ``'regular'`` or ``None``. Default is ``None``.
+        Must be one of `original, `regular` or `None. Default is `None`.
     pe_period:
-        If using the ``'regular'` pe, then we can define the period. Default is ``24``.
+        If using the ``regular`` pe, then we can define the period. Default is ``24``.
     """
 
     def __init__(self,
@@ -64,7 +64,7 @@ def __init__(self,
                  dropout: float = 0.3,
                  chunk_mode: str = 'chunk',
                  pe: str = None,
-                 pe_period: int = 24):
+                 pe_period: int = None):
         """Create transformer structure from Encoder and Decoder blocks."""
         super().__init__()
 
@@ -95,7 +95,9 @@ def __init__(self,
 
         if pe in pe_functions.keys():
             self._generate_PE = pe_functions[pe]
-            self._pe_period = pe_period
+
+            if pe == 'regular' and pe_period is not None:
+                self._pe_period = pe_period
         elif pe is None:
             self._generate_PE = None
         else: