diff --git a/lib/ft8/filt8.f90 b/lib/ft8/filt8.f90
index aeacf2a74..abe797ba7 100644
--- a/lib/ft8/filt8.f90
+++ b/lib/ft8/filt8.f90
@@ -9,7 +9,7 @@ subroutine filt8(f0,nslots,width,wave)
   equivalence (x,cx)
 
   x=wave
-  call four2a(x,NFFT,1,-1,0)              !r2c
+  call four2a(cx,NFFT,1,-1,0)              !r2c
   df=12000.0/NFFT
   fa=f0 - 0.5*6.25
   fb=f0 + 7.5*6.25 + (nslots-1)*60.0