diff --git a/iota/types.py b/iota/types.py
index 70372f9..26b25ed 100644
--- a/iota/types.py
+++ b/iota/types.py
@@ -49,7 +49,7 @@ class TryteString(JsonSerializable):
   IMPORTANT: A TryteString does not represent a numeric value!
   """
   @classmethod
-  def random(cls, length):
+  def random(cls, length=None):
     # type: (int) -> TryteString
     """
     Generates a random sequence of trytes.
@@ -60,6 +60,16 @@ def random(cls, length):
     alphabet  = list(itervalues(AsciiTrytesCodec.alphabet))
     generator = SystemRandom()
 
+    try:
+      if length is None:
+        length = cls.LEN
+
+      if length <= 0:
+        raise TypeError("length parameter needs to be greater than zero")
+    except AttributeError:  # class has no LEN attribute
+      if length is None:
+        raise TypeError("{class_name} does not define a length property".format(class_name=cls.__name__))
+
     # :py:meth:`SystemRandom.choices` wasn't added until Python 3.6;
     # for compatibility, we will continue to use ``choice`` in a loop.
     # https://docs.python.org/3/library/random.html#random.choices