diff --git a/README.md b/README.md
index 30284b5..3d72df7 100644
--- a/README.md
+++ b/README.md
@@ -20,7 +20,7 @@ connections
 The BusVoodoo provides:
 
 - a USB port for a connection to the PC
-- a I/O port for the 0-5V protocols
+- an I/O port for the 0-5V protocols
 - an I2C port to control an OLED display
 - a programming port for debugging usindg SWD and UART