Midrasch zu Bereschit 41:18

And Pharaoh said unto Joseph: “I have dreamed a dream (ibid.). As he was about to relate the dream to him, he decided to test Joseph by altering the dream slightly. He said: “Seven kine went up out of the Nile, fat and well-formed,” whereupon Joseph replied: “That is not so, you saw fat and healthy kine.” “And there were,” he said to him, “seven lean and ill-favored kine.” And Joseph replied: “You did not see this but rather ugly-appearing and thin-fleshed kine.” “And there were seven full and good ears of corn,” he continued. Whereupon Joseph answered: “That too is not so, you saw fat and good ones.” “There were seven shrunken ears of corn,” he added. And Joseph responded: “That is not so, you beheld seven ears of corn, withered thin and blistered by the east wind.” Pharaoh began to wonder about this. He said to him: “You must have been behind me when I had my dream,” as it is said: For inasmuch as God hath shown thee all this, there is none so discreet and wise as thou (ibid. v. 39).