diff --git a/lib/fast_decode.f90 b/lib/fast_decode.f90
index eebb73108..c3cadb6a7 100644
--- a/lib/fast_decode.f90
+++ b/lib/fast_decode.f90
@@ -1,4 +1,4 @@
-subroutine fast_decode(id2,narg,ntrperiod,line,mycall_12,   &
+subroutine fast_decode(id2,narg,trperiod,line,mycall_12,   &
      hiscall_12)
 
   parameter (NMAX=30*12000)
@@ -6,6 +6,7 @@ subroutine fast_decode(id2,narg,ntrperiod,line,mycall_12,   &
   integer*2 id2a(NMAX)
   integer*2 id2b(NMAX)
   integer narg(0:14)
+  double precision trperiod
   real dat(30*12000)
   complex cdat(262145),cdat2(262145)
   real psavg(450)
@@ -41,7 +42,7 @@ subroutine fast_decode(id2,narg,ntrperiod,line,mycall_12,   &
   nhashcalls=narg(12)
 
   line(1:100)(1:1)=char(0)
-  if(t0.gt.float(ntrperiod)) go to 900
+  if(t0.gt.trperiod) go to 900
   if(t0.gt.t1) go to 900
 
   if(nmode.eq.102) then
@@ -53,7 +54,7 @@ subroutine fast_decode(id2,narg,ntrperiod,line,mycall_12,   &
      cdat2=cdat
      ndat=ndat0
      call wav11(id2,ndat,dat)
-     nzz=11025*ntrperiod
+     nzz=11025*int(trperiod)    !beware if fractional T/R period ever used here
      if(ndat.lt.nzz) dat(ndat+1:nzz)=0.0
      ndat=min(ndat,30*11025)
      call ana932(dat,ndat,cdat,npts)          !Make downsampled analytic signal
diff --git a/widgets/mainwindow.cpp b/widgets/mainwindow.cpp
index b11e7f9bb..cf165d0df 100644
--- a/widgets/mainwindow.cpp
+++ b/widgets/mainwindow.cpp
@@ -147,7 +147,7 @@ extern "C" {
                 float* level, float* sigdb, float* snr, float* dfreq,
                 float* width);
 
-  void fast_decode_(short id2[], int narg[], int* ntrperiod,
+  void fast_decode_(short id2[], int narg[], double * trperiod,
                     char msg[], char mycall[], char hiscall[],
                     fortran_charlen_t, fortran_charlen_t, fortran_charlen_t);
   void degrade_snr_(short d2[], int* n, float* db, float* bandwidth);
@@ -2965,10 +2965,9 @@ void MainWindow::decode()                                       //decode()
     narg[12]=0;
     narg[13]=-1;
     narg[14]=m_config.aggressive();
-    int nTRperiod=m_TRperiod;
     memcpy(d2b,dec_data.d2,2*360000);
     watcher3.setFuture (QtConcurrent::run (std::bind (fast_decode_,&d2b[0],
-        &narg[0],&nTRperiod,&m_msg[0][0],
+        &narg[0],&m_TRperiod,&m_msg[0][0],
         dec_data.params.mycall,dec_data.params.hiscall,8000,12,12)));
   } else {
     memcpy(to, from, qMin(mem_jt9->size(), size));