diff --git a/src/Functional/Maximum.php b/src/Functional/Maximum.php
index f2c4596f..439e3d85 100644
--- a/src/Functional/Maximum.php
+++ b/src/Functional/Maximum.php
@@ -17,7 +17,7 @@
  * Returns the maximum value of a collection
  *
  * @param Traversable|array $collection
- * @return integer|float
+ * @return integer|float|null
  */
 function maximum($collection)
 {
diff --git a/src/Functional/Minimum.php b/src/Functional/Minimum.php
index d0d67fb8..7281b76f 100644
--- a/src/Functional/Minimum.php
+++ b/src/Functional/Minimum.php
@@ -17,7 +17,7 @@
  * Returns the minimum value of a collection
  *
  * @param Traversable|array $collection
- * @return integer|float
+ * @return integer|float|null
  */
 function minimum($collection)
 {