The full case caption appears at the end of this opinion.
Posner, Circuit Judge. The plaintiff in this Title VII case appeals from a series of pretrial rulings that resulted in judgment for his employer. In a unit of eight or ten employees assembling radio amplifiers, Johnson was the only male and also the only American Indian. He contends (we must assume, for purposes of the appeal, truthfully) that during a period of two weeks prior to September 8, 1998, some of his coworkers made fun of his ethnicity by speaking to each other in a stereotypical Indian manner. There was a crescendo of this talk on September 8 that resulted in a shouting match between Johnson and one of the women. The two complained about each other to the company’s human resources department, which warned both of them that they would be disciplined if there were further incidents. There were none. The contention that the company is guilty of ethnic harassment is frivolous. Even if, as we greatly doubt, the offensive and gratuitous mockery of Johnson’s ethnicity reached the degree of severity at which it could be said to have altered his working conditions, Harris v. Forklift Systems, Inc., 510 U.S. 17, 21 (1993), the company, as soon as it was apprised of the situation, took prompt and entirely effective measures to stop it, thus discharging its legal duty. E.g., Berry v. Delta Airlines, Inc. , 260 F.3d 803, 813 (7th Cir. 2001); Tutman v. WBBM- TV/CBS, Inc. , 209 F.3d 1044, 1048 (7th Cir. 2000); Watts v. Kroger Co. , 147 F.3d 460, 465-66 (5th Cir. 1998).