diff --git a/src/casci.f90 b/src/casci.f90
index c1df266..25e2da2 100644
--- a/src/casci.f90
+++ b/src/casci.f90
@@ -137,6 +137,9 @@ SUBROUTINE casci
         key = 'nroot'
         write (unit_cidata) key
         write (unit_cidata) nroot
+        key = 'totsym'
+        write (unit_cidata) key
+        write (unit_cidata) totsym
         key = 'ecas'
         write (unit_cidata) key
         write (unit_cidata) ecas(1:nroot)
diff --git a/src/read_cidata.f90 b/src/read_cidata.f90
index bd9515b..49cc865 100644
--- a/src/read_cidata.f90
+++ b/src/read_cidata.f90
@@ -12,7 +12,7 @@ subroutine read_cidata
     character(len=len_convert_int_to_chr) :: chr_totsym
     character(:), allocatable :: filename
     integer :: unit, i, dict_cas_idx_size
-    integer :: ninact_read, nact_read, nsec_read, nelec_read, nroot_read
+    integer :: ninact_read, nact_read, nsec_read, nelec_read, nroot_read, totsym_read
     integer(kind=int64), allocatable :: dict_cas_idx_values(:)
     real(8), allocatable    :: ecas(:)
 
@@ -23,6 +23,7 @@ subroutine read_cidata
     call add_essential_input("nelec")
     call add_essential_input("ndet")
     call add_essential_input("nroot")
+    call add_essential_input("totsym")
     call add_essential_input("ecas")
     call add_essential_input("dict_cas_idx_values")
     call add_essential_input("ci_coefficients")
@@ -84,6 +85,14 @@ subroutine read_cidata
                 call stop_with_errorcode(1)
             end if
             call update_esesential_input(trim(adjustl(key)), .true.)
+        case ("totsym")
+            read (unit) totsym_read
+            if (totsym_read /= totsym) then
+                if (rank == 0) print *, "Error: Invalid totsym in cidata file. totsym in cidata = ", totsym_read, &
+                    " totsym = ", totsym
+                call stop_with_errorcode(1)
+            end if
+            call update_esesential_input(trim(adjustl(key)), .true.)
         case ("ecas")
             if (.not. essential_input_is_specified("nroot")) then
                 if (rank == 0) print *, "Error: ecas detected before nroot."