diff --git a/application/forms/TimeRangePicker/CustomForm.php b/application/forms/TimeRangePicker/CustomForm.php
index 8627267..7b37022 100644
--- a/application/forms/TimeRangePicker/CustomForm.php
+++ b/application/forms/TimeRangePicker/CustomForm.php
@@ -100,8 +100,8 @@ class CustomForm extends Form
         if ($start > $end) {
             $absoluteRangeParameters = TimeRangePickerTools::getAbsoluteRangeParameters();
             $this->getRedirectUrl()->getParams()
-                ->set($absoluteRangeParameters['start'], $end)
-                ->set($absoluteRangeParameters['end'], $start);
+                ->set($absoluteRangeParameters['start'], (string) $end)
+                ->set($absoluteRangeParameters['end'], (string) $start);
         }
 
         $this->getRedirectUrl()->remove(TimeRangePickerTools::getRelativeRangeParameter());
diff --git a/library/Graphite/Graphing/Chart.php b/library/Graphite/Graphing/Chart.php
index ded8ae8..bee5e7d 100644
--- a/library/Graphite/Graphing/Chart.php
+++ b/library/Graphite/Graphing/Chart.php
@@ -107,9 +107,9 @@ class Chart
         $response
             ->setHeader('Content-Type', 'image/png', true)
             ->setHeader('Content-Disposition', 'inline; filename="graph.png"', true)
-            ->setHeader('Cache-Control', null, true)
-            ->setHeader('Expires', null, true)
-            ->setHeader('Pragma', null, true)
+            ->setHeader('Cache-Control', '', true)
+            ->setHeader('Expires', '', true)
+            ->setHeader('Pragma', '', true)
             ->setBody($image)
             ->sendResponse();
 
diff --git a/library/Graphite/ProvidedHook/Icingadb/HostDetailExtension.php b/library/Graphite/ProvidedHook/Icingadb/HostDetailExtension.php
index 31e4e6c..94d5547 100644
--- a/library/Graphite/ProvidedHook/Icingadb/HostDetailExtension.php
+++ b/library/Graphite/ProvidedHook/Icingadb/HostDetailExtension.php
@@ -23,8 +23,8 @@ class HostDetailExtension extends HostDetailExtensionHook
         }
 
         $graphs = (string) Graphs::forIcingadbObject($host)
-            ->setWidth(440)
-            ->setHeight(220)
+            ->setWidth('440')
+            ->setHeight('220')
             ->setClasses(['object-detail-view'])
             ->setPreloadDummy()
             ->setShowNoGraphsFound(false)
diff --git a/library/Graphite/ProvidedHook/Icingadb/ServiceDetailExtension.php b/library/Graphite/ProvidedHook/Icingadb/ServiceDetailExtension.php
index 63c2b79..0f4f33a 100644
--- a/library/Graphite/ProvidedHook/Icingadb/ServiceDetailExtension.php
+++ b/library/Graphite/ProvidedHook/Icingadb/ServiceDetailExtension.php
@@ -23,8 +23,8 @@ class ServiceDetailExtension extends ServiceDetailExtensionHook
         }
 
         $graphs = (string) Graphs::forIcingadbObject($service)
-            ->setWidth(440)
-            ->setHeight(220)
+            ->setWidth('440')
+            ->setHeight('220')
             ->setClasses(['object-detail-view'])
             ->setPreloadDummy()
             ->setShowNoGraphsFound(false)
diff --git a/library/Graphite/ProvidedHook/Monitoring/DetailviewExtension.php b/library/Graphite/ProvidedHook/Monitoring/DetailviewExtension.php
index d6a4673..23912a7 100644
--- a/library/Graphite/ProvidedHook/Monitoring/DetailviewExtension.php
+++ b/library/Graphite/ProvidedHook/Monitoring/DetailviewExtension.php
@@ -20,8 +20,8 @@ class DetailviewExtension extends DetailviewExtensionHook
         }
 
         $graphs = (string) Graphs::forMonitoredObject($object)
-            ->setWidth(440)
-            ->setHeight(220)
+            ->setWidth('440')
+            ->setHeight('220')
             ->setClasses(['object-detail-view'])
             ->setPreloadDummy()
             ->setShowNoGraphsFound(false)
diff --git a/library/Graphite/Web/Widget/GraphImage.php b/library/Graphite/Web/Widget/GraphImage.php
index af64e69..e99bf09 100644
--- a/library/Graphite/Web/Widget/GraphImage.php
+++ b/library/Graphite/Web/Widget/GraphImage.php
@@ -126,7 +126,7 @@ class GraphImage extends AbstractWidget
                         // Try to render a higher time range, but give up
                         // once our default (1h) has been reached (non successfully).
                         if ($diff < 3600) {
-                            $url->setParam('from', $until - $diff * 2);
+                            $url->setParam('from', sprintf('%F', ($until - $diff * 2)));
                             continue;
                         }
                     }
diff --git a/library/Graphite/Web/Widget/Graphs.php b/library/Graphite/Web/Widget/Graphs.php
index c12a5d9..9ec8385 100644
--- a/library/Graphite/Web/Widget/Graphs.php
+++ b/library/Graphite/Web/Widget/Graphs.php
@@ -331,7 +331,7 @@ abstract class Graphs extends AbstractWidget
                                     ->setParam('height', $actheight);
 
                                 if (! $this->compact) {
-                                    $imageUrl->setParam('legend', 1);
+                                    $imageUrl->setParam('legend', '1');
                                 }
 
                                 if ($this->preloadDummy) {