HTTPOptions Error

const httpOptions = {
  headers: new HttpHeaders({ 'Content-Type': 'application/json'}),
  responseType: 'text' as 'text'
};

return this.http.post<string>(this.registrationUrl, JSON.stringify(form), httpOptions);

ERROR in ../../players/players-register/players-register.service.ts(37,82): error TS2345: Argument of type '{ headers: HttpHeaders; responseType: "text"; }' is not assignable to parameter of type '{ headers?: HttpHeaders | { [header: string]: string | string[]; }; observe?: "body"; params?: HttpParams | { [param: string]: string | string[]; }; reportProgress?: boolean; responseType?: "json"; withCredentials?: boolean; }'.
  Types of property 'responseType' are incompatible.
    Type '"text"' is not assignable to type '"json"'.
tournaments-create.service.ts(23,74): error TS2345: Argument of type '{ headers: HttpHeaders; responseType: "text"; }' is not assignable to parameter of type '{ headers?: HttpHeaders | { [header: string]: string | string[]; }; observe?: "body"; params?: HttpParams | { [param: string]: string | string[]; }; reportProgress?: boolean; responseType?: "json"; withCredentials?: boolean; }'.
  Types of property 'responseType' are incompatible.
    Type '"text"' is not assignable to type '"json"'.