diff --git a/webapp/frontend/src/app/modules/dashboard/dashboard.component.ts b/webapp/frontend/src/app/modules/dashboard/dashboard.component.ts
index 5ff4203..3a9b246 100644
--- a/webapp/frontend/src/app/modules/dashboard/dashboard.component.ts
+++ b/webapp/frontend/src/app/modules/dashboard/dashboard.component.ts
@@ -200,8 +200,9 @@ export class DashboardComponent implements OnInit, AfterViewInit, OnDestroy
                     format: 'MMM dd, yyyy HH:mm:ss'
                 },
                 y    : {
+
                     formatter: (value) => {
-                        return TemperaturePipe.formatTemperature(value, this.config.temperatureUnit, true);
+                        return TemperaturePipe.formatTemperature(value, this.config.temperatureUnit, true) as string;
                     }
                 }
             },
diff --git a/webapp/frontend/src/app/shared/temperature.pipe.ts b/webapp/frontend/src/app/shared/temperature.pipe.ts
index 1c6cebc..5ef1dae 100644
--- a/webapp/frontend/src/app/shared/temperature.pipe.ts
+++ b/webapp/frontend/src/app/shared/temperature.pipe.ts
@@ -7,7 +7,7 @@ export class TemperaturePipe implements PipeTransform {
     static celsiusToFahrenheit(celsiusTemp: number): number {
         return celsiusTemp * 9.0 / 5.0 + 32;
     }
-    static formatTemperature(celsiusTemp: number, unit: string, includeUnits: boolean): unknown {
+    static formatTemperature(celsiusTemp: number, unit: string, includeUnits: boolean): number|string {
         let convertedTemp
         let convertedUnitSuffix
         switch (unit) {
@@ -27,7 +27,7 @@ export class TemperaturePipe implements PipeTransform {
         }
     }
 
-  transform(celsiusTemp: number, unit = 'celsius', includeUnits = false): unknown {
+  transform(celsiusTemp: number, unit = 'celsius', includeUnits = false): number|string {
         return TemperaturePipe.formatTemperature(celsiusTemp, unit, includeUnits)
   }