diff --git a/lib/superfox/sfox_sync.f90 b/lib/superfox/sfox_sync.f90
index e91da4494..0149a8b2b 100644
--- a/lib/superfox/sfox_sync.f90
+++ b/lib/superfox/sfox_sync.f90
@@ -34,12 +34,13 @@ subroutine sfox_sync(crcvd,fsample,isync,f,t)
 
   pmax=0.
   ntol=100
-  iz=nint(ntol/df)
+  iz=nint(ntol/df)+2
   i0=nint(1500.0/df)
   ipk=-999
   jpk=-999
   jz=nsz-8*NS
   allocate(ccf(-iz:iz,1:jz))
+  ccf=0.
   do j=1,jz
      do i=-iz,iz
         p=0.