diff --git a/README.md b/README.md
index 08482f7..30548e8 100644
--- a/README.md
+++ b/README.md
@@ -3,7 +3,7 @@
 This is a script to control 4-pin PWM fans on ASRock Rack motherboards with IPMI. The BMC does not properly expose fan control, so they must be controlled using raw IPMI commands. This script is a user-friendly way to do that.
 
 
-    usage: asrock-pwm-ipmi [-h] [-i] [FAN:SPEED [FAN:SPEED ...]]
+    usage: asrock-pwm-ipmi [-h] [-i] [-a] [FAN:SPEED [FAN:SPEED ...]]
 
     Read information about and control fans on ASRock boards with IPMI.