diff --git a/lib/jekyll-github-metadata/metadata_drop.rb b/lib/jekyll-github-metadata/metadata_drop.rb
index 76f6535..af5f6bd 100644
--- a/lib/jekyll-github-metadata/metadata_drop.rb
+++ b/lib/jekyll-github-metadata/metadata_drop.rb
@@ -8,6 +8,9 @@ class MetadataDrop < Jekyll::Drops::Drop
 
       mutable true
 
+      # See https://github.com/jekyll/jekyll/pull/6338
+      alias_method :invoke_drop, :[]
+
       def to_s
         require "json"
         JSON.pretty_generate to_h
diff --git a/spec/site_github_munger_spec.rb b/spec/site_github_munger_spec.rb
index 3d765d8..0de9287 100644
--- a/spec/site_github_munger_spec.rb
+++ b/spec/site_github_munger_spec.rb
@@ -43,11 +43,11 @@
       let(:github_namespace) { { "source" => { "branch" => "foo" } } }
 
       it "lets user-specified values override the drop" do
-        expect(site.config["github"]["source"]["branch"]).to eql("foo")
+        expect(site.config["github"].invoke_drop("source")["branch"]).to eql("foo")
       end
 
       it "still sets other values" do
-        expect(site.config["github"]["source"]["path"]).to eql("/")
+        expect(site.config["github"].invoke_drop("source")["path"]).to eql("/")
       end
     end