diff --git a/README.md b/README.md
index 61ff9be15a..0290b153ba 100644
--- a/README.md
+++ b/README.md
@@ -110,7 +110,7 @@ The implementation supports the entire Arduino SPI API including transactions, e
 
 APIs related to deep sleep and watchdog timer are available in the ```ESP``` object.
 
-```ESP.deepSleep(microseconds, mode)``` will put the chip into deep sleep. ```mode``` is one of ```WAKE_DEFAULT```, ```WAKE_RFCAL```, ```WAKE_NO_RFCAL```, ```WAKE_RF_DISABLED```.
+```ESP.deepSleep(microseconds, mode)``` will put the chip into deep sleep. ```mode``` is one of ```WAKE_DEFAULT```, ```WAKE_RFCAL```, ```WAKE_NO_RFCAL```, ```WAKE_RF_DISABLED```. (GPIO16 needs to be tied to RST to wake from deepSleep.)
 
 ```ESP.wdtEnable()```, ```ESP.wdtDisable()```, and ```ESP.wdtFeed()``` provide some control over the watchdog timer.