diff --git a/docs/programming-guide.md b/docs/programming-guide.md
index 06e4c4ce527e..b09d6347cd1b 100644
--- a/docs/programming-guide.md
+++ b/docs/programming-guide.md
@@ -975,8 +975,8 @@ for details.
   <td> Return an array with the first <i>n</i> elements of the dataset. Note that this is currently not executed in parallel. Instead, the driver program computes all the elements. </td>
 </tr>
 <tr>
-  <td> <b>takeSample</b>(<i>withReplacement</i>, <i>num</i>, <i>seed</i>) </td>
-  <td> Return an array with a random sample of <i>num</i> elements of the dataset, with or without replacement, using the given random number generator seed. </td>
+  <td> <b>takeSample</b>(<i>withReplacement</i>, <i>num</i>, [<i>seed</i>]) </td>
+  <td> Return an array with a random sample of <i>num</i> elements of the dataset, with or without replacement, optionally pre-specifying a random number generator seed.</td>
 </tr>
 <tr>
   <td> <b>takeOrdered</b>(<i>n</i>, <i>[ordering]</i>) </td>