(FM-3701) Update README for is_a

diff --git a/README.markdown b/README.markdown
index 27dd0a71e4c3af962ef5e27c1bd561dddbdfe886..f91932365f927d5cf331f321a1b27a402f8a625b 100644 (file)
--- a/README.markdown
+++ b/README.markdown
@@ -405,7 +405,7 @@ Returns an array an intersection of two. For example, `intersection(["a","b","c"
 
 #### `is_a`
 
-Boolean check to determine whether a variable is of a given data type. This is equivalent to the `=~` type checks.
+Boolean check to determine whether a variable is of a given data type. This is equivalent to the `=~` type checks. This function is only available in Puppet 4, or when using the "future" parser. 
 
   ~~~
   foo = 3