diff --git a/map65/libm65/q65b.f90 b/map65/libm65/q65b.f90
index dbc0ebb4f..f23c2e001 100644
--- a/map65/libm65/q65b.f90
+++ b/map65/libm65/q65b.f90
@@ -68,7 +68,7 @@ subroutine q65b(nutc,nqd,fcenter,nfcal,nfsample,ikhz,mousedf,ntol,xpol,  &
   k0=nint((ipk*df3-1000.0)/df)
   if(nagain.eq.1) k0=nint((f_mouse-1000.0)/df)
 
-  if(k0.lt.nh .or. k0.gt.nfft1-nh) go to 900
+  if(k0.lt.nh .or. k0.gt.MAXFFT1-nfft2+1) go to 900
   if(snr1.lt.1.5) go to 900                      !### Threshold needs work? ###
 
   fac=1.0/nfft2