diff --git a/SoObjects/Appointments/SOGoAppointmentObject.m b/SoObjects/Appointments/SOGoAppointmentObject.m
index a15837e5b..661d823cc 100644
--- a/SoObjects/Appointments/SOGoAppointmentObject.m
+++ b/SoObjects/Appointments/SOGoAppointmentObject.m
@@ -2503,6 +2503,14 @@ inRecurrenceExceptionsForEvent: (iCalEvent *) theEvent
   
   rq = [_ctx request];
   rqCalendar = [iCalCalendar parseSingleFromSource: [rq contentAsString]];
+
+  // We are unable to parse the received calendar, we return right away
+  // with a 400 error code.
+  if (!rqCalendar)
+    {
+      return [NSException exceptionWithHTTPStatus: 400
+                                           reason: @"Unable to parse event."];
+    }
   
   if (![self isNew])
     {
diff --git a/SoObjects/Appointments/SOGoTaskObject.m b/SoObjects/Appointments/SOGoTaskObject.m
index 8bb4b500e..563f3fcbf 100644
--- a/SoObjects/Appointments/SOGoTaskObject.m
+++ b/SoObjects/Appointments/SOGoTaskObject.m
@@ -118,6 +118,15 @@
 
   rq = [_ctx request];
   rqCalendar = [iCalCalendar parseSingleFromSource: [rq contentAsString]];
+
+  // We are unable to parse the received calendar, we return right away
+  // with a 400 error code.
+  if (!rqCalendar)
+    {
+      return [NSException exceptionWithHTTPStatus: 400
+                                           reason: @"Unable to parse task."];
+    }
+
   [self adjustClassificationInRequestCalendar: rqCalendar];
   [rq setContent: [[rqCalendar versitString] dataUsingEncoding: [rq contentEncoding]]];