diff --git a/_assets/js/charting/business-data.js b/_assets/js/charting/business-data.js
index 9cfc78a..b6f36ad 100644
--- a/_assets/js/charting/business-data.js
+++ b/_assets/js/charting/business-data.js
@@ -184,7 +184,7 @@ Highcharts.wrap(Highcharts.PlotLineOrBand.prototype, 'render', function (proceed
       },{
         labels: { format: '{value} %' },
         opposite: true,
-        title: { text: undefined }
+        title: null
       }]
     });
   }
diff --git a/_assets/js/charting/global.js b/_assets/js/charting/global.js
index 1de824b..e191266 100644
--- a/_assets/js/charting/global.js
+++ b/_assets/js/charting/global.js
@@ -244,16 +244,16 @@
               x: 0,
               y: -5
             },
-            title: { text: null },
+            title: null,
           },{
             labels: {
               align: 'right',
               x: 0,
               y: -5
             },
-            title: { text: null }
+            title: null,
           }],
-          subtitle: { text: null }
+          subtitle: null
         }
       }]
     }
diff --git a/_assets/js/charting/heat.js b/_assets/js/charting/heat.js
index 45bd96b..0de1ed7 100644
--- a/_assets/js/charting/heat.js
+++ b/_assets/js/charting/heat.js
@@ -117,10 +117,10 @@
     yAxis: [{
       title: { text: "Leitungsnetz in km" }
     },{
-      title: { text: undefined },
+      title: null,
       opposite: true
     },{
-      title: { text: undefined },
+      title: null,
       opposite: true,
       labels: { format: "{value} %" },
       max: 20
diff --git a/_assets/js/charting/water.js b/_assets/js/charting/water.js
index 260811c..0d304af 100644
--- a/_assets/js/charting/water.js
+++ b/_assets/js/charting/water.js
@@ -111,10 +111,10 @@
     yAxis: [{
       title: { text: "Leitungsnetz in km" }
     },{
-      title: { text: undefined },
+      title: null,
       opposite: true
     },{
-      title: { text: undefined },
+      title: null,
       opposite: true,
       labels: { format: "{value} %" },
       max: 14