diff --git a/calendar/base/public/calIErrors.idl b/calendar/base/public/calIErrors.idl
index 56d65940564..c42e42252ac 100644
--- a/calendar/base/public/calIErrors.idl
+++ b/calendar/base/public/calIErrors.idl
@@ -61,5 +61,26 @@ interface calIErrors : nsISupports
    * An invalid or nonexistent timezone was encountered.
    */
   const unsigned long INVALID_TIMEZONE = ERROR_BASE + 1;
+
+
+  /* ICS specific errors */
+  const unsigned long ICS_ERROR_BASE = ERROR_BASE + 0x100;
+
+  /**
+   * ICS errors, copied from icalerror.h.
+   * The numbers (minus ICS_ERROR_BASE) should match with the enum
+   * values from icalerror.h
+   */
+  const unsigned long ICS_NO_ERROR = ICS_ERROR_BASE + 0;
+  const unsigned long ICS_BADARG = ICS_ERROR_BASE + 1;
+  const unsigned long ICS_NEWFAILED = ICS_ERROR_BASE + 2;
+  const unsigned long ICS_ALLOCATION = ICS_ERROR_BASE + 3;
+  const unsigned long ICS_MALFORMEDDATA = ICS_ERROR_BASE + 4;
+  const unsigned long ICS_PARSE = ICS_ERROR_BASE + 5;
+  const unsigned long ICS_INTERNAL = ICS_ERROR_BASE + 6;
+  const unsigned long ICS_FILE = ICS_ERROR_BASE + 7;
+  const unsigned long ICS_USAGE = ICS_ERROR_BASE + 8;
+  const unsigned long ICS_UNIMPLEMENTED = ICS_ERROR_BASE + 9;
+  const unsigned long ICS_UNKNOWN = ICS_ERROR_BASE + 10;
 };
 
diff --git a/calendar/base/src/calICSService.cpp b/calendar/base/src/calICSService.cpp
index 357ef1000b8..cd49bfcae39 100644
--- a/calendar/base/src/calICSService.cpp
+++ b/calendar/base/src/calICSService.cpp
@@ -49,6 +49,7 @@
 
 #include "calIEvent.h"
 #include "calBaseCID.h"
+#include "calIErrors.h"
 
 static NS_DEFINE_CID(kCalICSService, CAL_ICSSERVICE_CID);
 
@@ -964,7 +965,9 @@ calICSService::ParseICS(const nsACString& serialized,
                 PromiseFlatCString(serialized).get(), icalerrno,
                 icalerror_strerror(icalerrno));
 #endif
-        return NS_ERROR_FAILURE;
+        // The return values is calIError match with ical errors,
+        // so no need for a conversion table or anything.
+        return calIErrors::ICS_ERROR_BASE + icalerrno;
     }
     calIcalComponent *comp = new calIcalComponent(ical, nsnull);
     if (!comp) {