diff --git a/features/frontmatter_defaults.feature b/features/frontmatter_defaults.feature
index c3e7c8de..41a7a35e 100644
--- a/features/frontmatter_defaults.feature
+++ b/features/frontmatter_defaults.feature
@@ -128,3 +128,9 @@ Feature: frontmatter defaults
     When I run jekyll build
     Then the _site directory should exist
     And I should see "Value: Override" in "_site/slides/slide2.html"
+
+  Scenario: Deep merge frontmatter defaults
+    Given I have an "index.html" page with fruit "{orange: 1}" that contains "Fruits: {{ page.fruit.orange | plus: page.fruit.apple }}"
+    And I have a configuration file with "defaults" set to "[{scope: {path: ""}, values: {fruit: {apple: 2}}}]"
+    When I run jekyll build
+    Then I should see "Fruits: 3" in "_site/index.html"
diff --git a/lib/jekyll/frontmatter_defaults.rb b/lib/jekyll/frontmatter_defaults.rb
index 2c5755b5..42b85ed5 100644
--- a/lib/jekyll/frontmatter_defaults.rb
+++ b/lib/jekyll/frontmatter_defaults.rb
@@ -41,10 +41,10 @@ module Jekyll
         old_scope = nil
         matching_sets(path, type).each do |set|
           if has_precedence?(old_scope, set['scope'])
-            defaults.merge! set['values']
+            defaults = Utils.deep_merge_hashes(defaults, set['values'])
             old_scope = set['scope']
           else
-            defaults = set['values'].merge(defaults)
+            defaults = Utils.deep_merge_hashes(set['values'], defaults)
           end
         end
         defaults
@@ -145,4 +145,4 @@ module Jekyll
       end
     end
   end
-end
\ No newline at end of file
+end