diff --git a/README.md b/README.md
index e1a682e5318c1dbcaf9ff9595ebf734e17166732..716be978538045115d4384bc0f629e21cb5ecb70 100644
--- a/README.md
+++ b/README.md
@@ -40,7 +40,7 @@ Package Installation
 ---------------------------------
 While the dataRetreival package is in development (and not on CRAN), the zoo package must first be manually installed. To install the dataRetrieval package, you must be using R 3.0 or greater and run the following commands:
 
-	install.packages(c("zoo","XML","RCurl))
+	install.packages(c("zoo","XML","RCurl","plyr"))
 	install.packages("dataRetrieval", repos="http://usgs-r.github.com")