diff --git a/README.md b/README.md
index 5274ad1..996e634 100644
--- a/README.md
+++ b/README.md
@@ -90,7 +90,7 @@ GPIO PINS:
 <br>14, 2 & 15 should also be available if you are not using the SD Card. 
 <br>You can also use pins 1 and 3 if you do not use Serial. 
 <br>More info: https://randomnerdtutorials.com/esp32-cam-ai-thinker-pinout/
-<br>BTW-You can use an MCP23017 io expander chip on pins 12 and 13 to give you 16 general purpose gpio pins.  
+<br>BTW-You can use an MCP23017 io expander chip on pins 12 and 13 to give you 16 general purpose gpio pins, this requires the adafruit MCP23017 library to be installed.
 <br>Pin 16 is used for psram but you may get away with using it as input for a button etc.?