diff --git a/modules/statistics/lib/Aggregator.php b/modules/statistics/lib/Aggregator.php
index 345b446385b102d33e90d701c2bd0ef2eab8b5b0..9be2b4e2d441ecd574f9479394754e0db282d011 100644
--- a/modules/statistics/lib/Aggregator.php
+++ b/modules/statistics/lib/Aggregator.php
@@ -113,17 +113,34 @@ class sspmod_statistics_Aggregator {
 			foreach ($ruleresults AS $fileno => $fileres) {
 			
 				$slotlist = array_keys($fileres);
+				
+				$maxslot = $slotlist[count($slotlist)-1];
+				#print_r($slotlist); 
 		
 				// Get start and end slot number within the file, based on the fileslot.
-				$start = $datehandler->toSlot($datehandler->fromSlot($fileno, $this->statrules[$rulename]['fileslot']), $this->statrules[$rulename]['slot']);
-				$end = $datehandler->toSlot($datehandler->fromSlot($fileno+1, $this->statrules[$rulename]['fileslot']), $this->statrules[$rulename]['slot']);
+				$start = (int)$datehandler->toSlot($datehandler->fromSlot($fileno, $this->statrules[$rulename]['fileslot']), $this->statrules[$rulename]['slot']);
+				$end = (int)$datehandler->toSlot($datehandler->fromSlot($fileno+1, $this->statrules[$rulename]['fileslot']), $this->statrules[$rulename]['slot']);
 		
 				// Fill in missing entries and sort file results
 				$filledresult = array();
 				for ($slot = $start; $slot < $end; $slot++) {
-					$filledresult[$slot] = (isset($fileres[$slot])) ? $fileres[$slot] : array('_' => 0);
+					#print_r(gettype($slot));
+					if (array_key_exists($slot,  $fileres)) {
+						$filledresult[$slot] = $fileres[$slot];
+					} else {
+						#echo('SLot [' . $slot . '] of [' . $maxslot . ']' . "\n");
+						if ($slot > $maxslot) {
+							$filledresult[$slot] = array('_' => -1);
+						} else {
+							$filledresult[$slot] = array('_' => NULL);
+						}				
+					}
+					#print_r($filledresult[$slot]);
+#					 = (isset($fileres[$slot])) ? $fileres[$slot] : array('_' => NULL);
 				}
 				
+				#print_r($filledresult); exit;
+				
 				// store file
 				file_put_contents($this->statdir . '/' . $rulename . '-' . $fileno . '.stat', serialize($filledresult), LOCK_EX );
 			}
diff --git a/modules/statistics/www/showstats.php b/modules/statistics/www/showstats.php
index 2f89002677e118da519bf60c9b7fe0fff89c6f2f..43ee123ae1841726612012a0784bdd7abd651560 100644
--- a/modules/statistics/www/showstats.php
+++ b/modules/statistics/www/showstats.php
@@ -156,6 +156,10 @@ $maxvaluetime = 0;
 $debugdata = array();
 
 
+
+/*
+ * Search for maximum value in order to scale the Y-scale of the graph presentation.
+ */
 $maxdelimiter = $delimiter;
 if (array_key_exists('graph.total', $statrules[$rule]) && $statrules[$rule]['graph.total'] === TRUE) {
 	$maxdelimiter = '_';
@@ -223,7 +227,11 @@ function getPercentValues($results, $delimiter) {
 	foreach($results AS $slot => $res) {
 		#echo ('<p>new value: ' . number_format(100*$res[$delimiter] / $max, 2));
 		if (array_key_exists($delimiter, $res)) {
-			$dataset[] = number_format(100*$res[$delimiter] / $max, 2);
+			if ($res[$delimiter] === -1) {
+				$dataset[] = -1;
+			} else {
+				$dataset[] = number_format(100*$res[$delimiter] / $max, 2);
+			}
 		} else {
 			$dataset[] = '0';
 		}
@@ -252,6 +260,8 @@ if ($delimiter !== '_') {
 	}
 }
 
+#echo('<pre>'); print_r($datasets); exit;
+
 #echo 'set axis on lastslot [' . $lastslot . ']';
 $axis[] =  $datehandler->prettyDateSlot($lastslot+1, $slotsize, $dateformat_intra); 
 #print_r($axis);