diff --git a/fhem/FHEM/13_KS300.pm b/fhem/FHEM/13_KS300.pm
index 0b4e6ae30..1d7c96c2a 100755
--- a/fhem/FHEM/13_KS300.pm
+++ b/fhem/FHEM/13_KS300.pm
@@ -173,20 +173,20 @@ KS300_Parse($$)
        # The code also handles counter resets after battery replacement
 
        my $rain_raw_delta= $rain_raw- $rain_raw_prev;
-       my $thours_delta= ($tsecs- $tsecs_prev)/3600.0; # in hours
-       my $rain_raw_per_hour= $rain_raw_delta/$thours_delta;
-       if(($rain_raw_delta<0) || ($rain_raw_per_hour> 200.0)) {
-          $rain_raw_ofs= $rain_raw_ofs_prev-$rain_raw_delta;
-          # If the switch in the tick count occurs simultaneously with an
-          # increase due to rain, the tick is lost. We therefore assume that
-          # offsets between -5 and 0 are indeed rain.
-          if(($rain_raw_ofs>=-5) && ($rain_raw_ofs<0)) { $rain_raw_ofs= 0; }
-          $r->{rain_raw_ofs}{TIME} = $tm;
-          $r->{rain_raw_ofs}{VAL} = $rain_raw_ofs;
-          $def->{CHANGED}[$n++] = "rain_raw_ofs: $rain_raw_ofs";
-
+       if($tsecs!= $tsecs_prev) { # avoids a rare but relevant condition
+            my $thours_delta= ($tsecs- $tsecs_prev)/3600.0; # in hours
+            my $rain_raw_per_hour= $rain_raw_delta/$thours_delta;
+            if(($rain_raw_delta<0) || ($rain_raw_per_hour> 200.0)) {
+                $rain_raw_ofs= $rain_raw_ofs_prev-$rain_raw_delta;
+                # If the switch in the tick count occurs simultaneously with an
+                # increase due to rain, the tick is lost. We therefore assume that
+                # offsets between -5 and 0 are indeed rain.
+                if(($rain_raw_ofs>=-5) && ($rain_raw_ofs<0)) { $rain_raw_ofs= 0; }
+                $r->{rain_raw_ofs}{TIME} = $tm;
+                $r->{rain_raw_ofs}{VAL} = $rain_raw_ofs;
+                $def->{CHANGED}[$n++] = "rain_raw_ofs: $rain_raw_ofs";
+            }
        }
-
        $rain_raw_adj= $rain_raw+ $rain_raw_ofs;
 
     }