diff --git a/features/collections.feature b/features/collections.feature
index 32e9161c..402e7dab 100644
--- a/features/collections.feature
+++ b/features/collections.feature
@@ -70,3 +70,15 @@ Feature: Collections
     When I run jekyll build
     Then the _site directory should exist
     And I should see "Collections: _methods/configuration.md _methods/sanitized_path.md _methods/site/generate.md _methods/site/initialize.md _methods/um_hi.md" in "_site/index.html"
+
+  Scenario: All the documents
+    Given I have an "index.html" page that contains "All documents: {% for doc in site.documents %}{{ doc.relative_path }} {% endfor %}"
+    And I have fixture collections
+    And I have a "_config.yml" file with content:
+    """
+    collections:
+    - methods
+    """
+    When I run jekyll build
+    Then the _site directory should exist
+    And I should see "All documents: _methods/configuration.md _methods/sanitized_path.md _methods/site/generate.md _methods/site/initialize.md _methods/um_hi.md" in "_site/index.html"
diff --git a/lib/jekyll/site.rb b/lib/jekyll/site.rb
index 5350edec..5ebf3c20 100644
--- a/lib/jekyll/site.rb
+++ b/lib/jekyll/site.rb
@@ -413,7 +413,7 @@ module Jekyll
     def documents
       collections.reduce(Set.new) do |docs, (_, collection)|
         docs.merge(collection.docs)
-      end
+      end.to_a
     end
 
     def each_site_file