 Curiously, this move, natural as it seems, is a serious mistake.
1. e2e4  1... e7e5  2. g1f3  2... b8c6  3. f1b5  3... g8f6  4. d2d3  4... f8c5  5. b1c3 One of the hundreds of ways to play the Anti-Berlin system. This is only the fifth most popular move. 5... e8g8  6. e1g1  6... f8e8 