diff --git a/CMakeLists.txt b/CMakeLists.txt
index ce311b4ee..cf89605f9 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -387,6 +387,7 @@ set (wsjt_FSRCS
   lib/fsk4hf/chkcrc10.f90
   lib/fsk4hf/chkcrc12.f90
   lib/ft8/chkcrc12a.f90
+  lib/ft8/chkcrc13a.f90
   lib/ft8/chkcrc14a.f90
   lib/chkcall.f90
   lib/chkhist.f90
diff --git a/lib/ft8/chkcrc13a.f90 b/lib/ft8/chkcrc13a.f90
new file mode 100644
index 000000000..74259cfcf
--- /dev/null
+++ b/lib/ft8/chkcrc13a.f90
@@ -0,0 +1,24 @@
+subroutine chkcrc13a(decoded,nbadcrc)
+
+  use crc
+  integer*1 decoded(90)
+  integer*1, target:: i1Dec8BitBytes(12)
+  character*90 cbits
+
+! Write decoded bits into cbits: 77-bit message plus 13-bit CRC
+  write(cbits,1000) decoded
+1000 format(90i1)
+  read(cbits,1001) i1Dec8BitBytes
+1001 format(12b8)
+  read(cbits,1002) ncrc13                         !Received CRC13
+1002 format(77x,b13)
+
+  i1Dec8BitBytes(10)=iand(i1Dec8BitBytes(10),128+64+32+16+8)
+  i1Dec8BitBytes(11:12)=0
+  icrc13=crc13(c_loc(i1Dec8BitBytes),12)          !CRC13 computed from 77 msg bits
+
+  nbadcrc=1
+  if(ncrc13.eq.icrc13) nbadcrc=0
+  
+  return
+end subroutine chkcrc13a