diff --git a/libraries/String.elm b/libraries/String.elm
index 8c0ef71..6f58843 100644
--- a/libraries/String.elm
+++ b/libraries/String.elm
@@ -32,7 +32,7 @@ import Native.String
 import Maybe (Maybe)
 
 {-| Check if a string is empty `(isEmpty "" == True)` -}
-isEmpty : String
+isEmpty : String -> Bool
 isEmpty = Native.String.isEmpty
 
 {-| Add a character to the beginning of a string -}
@@ -308,4 +308,4 @@ something.
       fromList ['a','b','c'] == "abc"
 -}
 fromList : String -> [Char]
-fromList = Native.String.fromList
\ No newline at end of file
+fromList = Native.String.fromList