diff --git a/collections/README.md b/collections/README.md
index 16b4b7d5c82f..52e85d654dae 100644
--- a/collections/README.md
+++ b/collections/README.md
@@ -398,7 +398,7 @@ console.assert(
 ### single
 
 Returns the only element in the given collection matching the given predicate.
-Returns undefined if there is none.
+Returns undefined if there is none or multiple matches for the predicate.
 
 ```ts
 import { single } from "https://deno.land/std@$STD_VERSION/collections/mod.ts";
diff --git a/collections/single.ts b/collections/single.ts
index 78438cef89ee..fb037a2232c1 100644
--- a/collections/single.ts
+++ b/collections/single.ts
@@ -1,7 +1,7 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
 
 /**
- * Returns the only element in the given collection matching the given predicate. Returns undefined if there is none.
+ * Returns the only element in the given collection matching the given predicate. Returns undefined if there is none or multiple matches for the predicate.
  *
  * Example:
  *