diff --git a/lib/ft4/ft4_decode.f90 b/lib/ft4/ft4_decode.f90
index 790553bd1..0c2630438 100644
--- a/lib/ft4/ft4_decode.f90
+++ b/lib/ft4/ft4_decode.f90
@@ -74,7 +74,7 @@ subroutine ft4_decode(cdatetime0,nfqso,iwave,ndecodes,mycall,hiscall,nrx,line)
    ndecodes=0
    do icand=1,ncand
       f0=candidate(1,icand)
-      xsnr=10*log10(candidate(3,icand))-15.0
+      xsnr=10*log10(candidate(3,icand))-18.0
       if( f0.le.375.0 .or. f0.ge.(5000.0-375.0) ) cycle
       call ft4_downsample(iwave,f0,cd2) ! downsample from 320 Sa/Symbol to 20 Sa/Symbol
       sum2=sum(cd2*conjg(cd2))/(20.0*76)