פירוש על עבודה זרה 92:9

The Talmud says that R. Akiva did not really come to this leniency by a midrashic inference. Rather, it was a tradition that R. Eliezer had taught him, but R. Eliezer forgot the teaching. His midrash was merely meant to remind R. Eliezer of his tradition. It was not formative.