diff --git a/lib/ft4/clockit.f90 b/lib/ft4/clockit.f90
index 17cb6ade1..a6306409e 100644
--- a/lib/ft4/clockit.f90
+++ b/lib/ft4/clockit.f90
@@ -103,7 +103,7 @@ subroutine clockit(dname,k)
 
   entry clockit2(data_dir)
   l1=index(data_dir,char(0))-1
-  data_dir(l1+1:l1+1)='/'
+  if(l1.ge.1) data_dir(l1+1:l1+1)='/'
   fname=data_dir(1:l1+1)//'clockit.out'
   return
   
diff --git a/lib/ft4/ft4_decode.f90 b/lib/ft4/ft4_decode.f90
index 6fd3a8fc3..6cdf01775 100644
--- a/lib/ft4/ft4_decode.f90
+++ b/lib/ft4/ft4_decode.f90
@@ -418,7 +418,7 @@ subroutine ft4_decode(cdatetime0,tbuf,nfa,nfb,nQSOProgress,ncontest,nfqso,iwave,
             write(line,1000) hhmmss,nsnr,tsig,nint(freq),message
 1000        format(a6,i4,f5.1,i5,' + ',1x,a37)
             l1=index(data_dir,char(0))-1
-            data_dir(l1+1:l1+1)="/"
+            if(l1.ge.1) data_dir(l1+1:l1+1)="/"
             fname=data_dir(1:l1+1)//'all_ft4.txt'
             open(24,file=trim(fname),status='unknown',position='append')
             write(24,1002) cdatetime0,nsnr,tsig,nint(freq),message,    &