diff --git a/pyplayready/exceptions.py b/pyplayready/exceptions.py
index 244aedf..18032a0 100644
--- a/pyplayready/exceptions.py
+++ b/pyplayready/exceptions.py
@@ -10,5 +10,9 @@ class InvalidSession(PyPlayredyException):
     """No Session is open with the specified identifier."""
 
 
+class InvalidInitData(PyPlayredyException):
+    """The Playready Cenc Header Data is invalid or empty."""
+
+
 class DeviceMismatch(PyPlayredyException):
     """The Remote CDMs Device information and the APIs Device information did not match."""
\ No newline at end of file
diff --git a/pyplayready/remotecdm.py b/pyplayready/remotecdm.py
index d38989a..251a3ee 100644
--- a/pyplayready/remotecdm.py
+++ b/pyplayready/remotecdm.py
@@ -11,7 +11,7 @@ from pyplayready.bcert import CertificateChain
 from pyplayready.ecc_key import ECCKey
 from pyplayready.pssh import PSSH
 
-from pyplayready.exceptions import (DeviceMismatch, )
+from pyplayready.exceptions import (DeviceMismatch, InvalidInitData)
 
 
 class RemoteCdm(Cdm):
@@ -104,7 +104,7 @@ class RemoteCdm(Cdm):
         if not pssh:
             raise InvalidInitData("A pssh must be provided.")
         if not isinstance(pssh, str):
-            raise InvalidInitData(f"Expected pssh to be a {PSSH}, not {pssh!r}")
+            raise InvalidInitData(f"Expected pssh to be a {str}, not {pssh!r}")
 
         r = self.__session.post(
             url=f"{self.host}/{self.device_name}/get_license_challenge",