diff --git a/README.md b/README.md
index cb6d93a..aab0640 100644
--- a/README.md
+++ b/README.md
@@ -355,7 +355,7 @@ f'{"abcde":10.3}'   # 'abc       '
 ### Number Options
 ```python
 f'{ 123456:10,}'    # '   123,456'
-'{ 123456:10_}'    # '   123_456'
+f'{ 123456:10_}'    # '   123_456'
 f'{ 123456:+10}'    # '   +123456'
 f'{-123456:=10}'    # '-   123456'
 f'{ 123456: }'      # ' 123456'