Index: openacs-4/packages/calendar/www/mini-calendar.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/calendar/www/mini-calendar.tcl,v
diff -u -r1.22 -r1.23
--- openacs-4/packages/calendar/www/mini-calendar.tcl	7 Aug 2017 23:48:05 -0000	1.22
+++ openacs-4/packages/calendar/www/mini-calendar.tcl	22 May 2018 16:44:55 -0000	1.23
@@ -85,7 +85,7 @@
 set day              [util::trim_leading_zeros [lindex $date_list 2]]
 
 set months_list      [dt_month_names]
-set curr_month_idx   [expr [util::trim_leading_zeros [clock format $now -format "%m"]]-1]
+set curr_month_idx   [expr {[util::trim_leading_zeros [clock format $now -format "%m"]]-1}]
 set curr_day         [clock format $now -format "%d"]
 set curr_month       [clock format $now -format "%B"]
 set curr_year        [clock format $now -format "%Y"]