diff --git a/projects/ngx-translate/core/src/lib/translate.pipe.ts b/projects/ngx-translate/core/src/lib/translate.pipe.ts
index b1f4ea3c..6d0abb35 100644
--- a/projects/ngx-translate/core/src/lib/translate.pipe.ts
+++ b/projects/ngx-translate/core/src/lib/translate.pipe.ts
@@ -37,7 +37,7 @@ export class TranslatePipe implements PipeTransform, OnDestroy {
     this.translate.get(key, interpolateParams).subscribe(onTranslation);
   }
 
-  transform(query: string, ...args: any[]): any {
+  transform(query: string | null | undefined, ...args: any[]): any {
     if (!query || !query.length) {
       return query;
     }