diff --git a/predictionio/__init__.py b/predictionio/__init__.py
index 01ac045..d70c85c 100644
--- a/predictionio/__init__.py
+++ b/predictionio/__init__.py
@@ -47,6 +47,10 @@
   pass
 
 
+class InvalidArgumentError(PredictionIOAPIError):
+    pass
+
+
 def event_time_validation(t):
   """ Validate event_time according to EventAPI Specification.
   """