diff --git a/lib/opdetmsk144.f90 b/lib/opdetmsk144.f90
index ef8a9a482..6fe57913d 100644
--- a/lib/opdetmsk144.f90
+++ b/lib/opdetmsk144.f90
@@ -80,7 +80,7 @@ subroutine opdetmsk144(cbig,n,lines,nmessages,nutc,ntol,t00)
   
     xmax=0.0
     bestf=0.0
-    do if=-200,200   ! search for frequency that maximizes sync correlation 
+    do if=-ntol,ntol   ! search for frequency that maximizes sync correlation 
       ferr=if
 ! shift analytic signal to baseband
       call tweak1(cdat,NPTS,-(1500+ferr),cdat2)