diff --git a/sphinx/ext/autosummary/__init__.py b/sphinx/ext/autosummary/__init__.py
index 3dded11ff..d4fd80467 100644
--- a/sphinx/ext/autosummary/__init__.py
+++ b/sphinx/ext/autosummary/__init__.py
@@ -325,7 +325,7 @@ class Autosummary(Directive):
             # -- Grab the summary
 
             documenter.add_content(None)
-            doc = list(documenter.process_doc([self.result.data]))
+            doc = self.result.data
 
             while doc and not doc[0].strip():
                 doc.pop(0)
diff --git a/tests/test_ext_autosummary.py b/tests/test_ext_autosummary.py
index 0aea99df6..8624153e2 100644
--- a/tests/test_ext_autosummary.py
+++ b/tests/test_ext_autosummary.py
@@ -73,6 +73,10 @@ def test_get_items_summary(app, status, warning):
 
     def handler(app, what, name, obj, options, lines):
         assert isinstance(lines, list)
+
+        # ensure no docstring is processed twice:
+        assert 'THIS HAS BEEN HANDLED' not in lines
+        lines.append('THIS HAS BEEN HANDLED')
     app.connect('autodoc-process-docstring', handler)
 
     sphinx.ext.autosummary.Autosummary.get_items = new_get_items