diff --git a/FSCalendar/FSCalendar.h b/FSCalendar/FSCalendar.h
index dca71e9..9a9bbdf 100644
--- a/FSCalendar/FSCalendar.h
+++ b/FSCalendar/FSCalendar.h
@@ -432,7 +432,7 @@ IB_DESIGNABLE
 /**
  A date object identifying the section of the selected date. (read-only)
  */
-@property (readonly, nonatomic) NSDate *selectedDate;
+@property (nullable, readonly, nonatomic) NSDate *selectedDate;
 
 /**
  The dates representing the selected dates. (read-only)