diff --git a/OpenChange/NSDate+MAPIStore.h b/OpenChange/NSDate+MAPIStore.h
index 0a01a2ddc..93f09be37 100644
--- a/OpenChange/NSDate+MAPIStore.h
+++ b/OpenChange/NSDate+MAPIStore.h
@@ -39,6 +39,6 @@
 
 @end
 
-NSComparisonResult NSDateCompare (NSDate *date1, NSDate *date2, void *);
+NSComparisonResult NSDateCompare (id date1, id date2, void *);
 
 #endif /* NSCALENDARDATE+MAPISTORE_H */
diff --git a/OpenChange/NSDate+MAPIStore.m b/OpenChange/NSDate+MAPIStore.m
index 1e631b82b..06e55f1d7 100644
--- a/OpenChange/NSDate+MAPIStore.m
+++ b/OpenChange/NSDate+MAPIStore.m
@@ -131,7 +131,7 @@ _setupRefDate ()
 @end
 
 NSComparisonResult
-NSDateCompare (NSDate *date1, NSDate *date2, void *ctx)
+NSDateCompare (id date1, id date2, void *ctx)
 {
   NSTimeInterval secs1, secs2;
   NSComparisonResult result;