diff --git a/src/lib/directives/ng2-fittext.directive.ts b/src/lib/directives/ng2-fittext.directive.ts
index 331783c..1c3709b 100644
--- a/src/lib/directives/ng2-fittext.directive.ts
+++ b/src/lib/directives/ng2-fittext.directive.ts
@@ -143,13 +143,13 @@ export class Ng2FittextDirective
   getStartFontSizeFromHeight(): number {
     return this.container
       ? this.container.clientHeight
-      : this.el.nativeElement.parentElement.clientHeight;
+      : this.el.nativeElement.parentElement!.clientHeight;
   }
 
   private getStartFontSizeFromWeight(): number {
     return this.container
       ? this.container.clientWidth
-      : this.el.nativeElement.parentElement.clientWidth;
+      : this.el.nativeElement.parentElement!.clientWidth;
   }
 
   isDone(): boolean {
@@ -164,7 +164,7 @@ export class Ng2FittextDirective
     return this.container
       ? this.checkOverflow(this.container, this.el.nativeElement)
       : this.checkOverflow(
-          this.el.nativeElement.parentElement,
+          this.el.nativeElement.parentElement!,
           this.el.nativeElement
         );
   }