diff --git a/gallery_dl/config.py b/gallery_dl/config.py
index 855fb4f7..f932e3a5 100644
--- a/gallery_dl/config.py
+++ b/gallery_dl/config.py
@@ -261,13 +261,19 @@ def accumulate(path, key, conf=_config):
         if key in conf:
             value = conf[key]
             if value:
-                result.extend(value)
+                if isinstance(value, list):
+                    result.extend(value)
+                else:
+                    result.append(value)
         for p in path:
             conf = conf[p]
             if key in conf:
                 value = conf[key]
                 if value:
-                    result[:0] = value
+                    if isinstance(value, list):
+                        result[:0] = value
+                    else:
+                        result.insert(0, value)
     except Exception:
         pass
     return result
diff --git a/gallery_dl/job.py b/gallery_dl/job.py
index be244279..f58cc05d 100644
--- a/gallery_dl/job.py
+++ b/gallery_dl/job.py
@@ -619,8 +619,6 @@ class DownloadJob(Job):
             pp_opts = cfg("postprocessor-options")
             pp_list = []
 
-            if isinstance(postprocessors, (dict, str)):
-                postprocessors = (postprocessors,)
             for pp_dict in postprocessors:
                 if isinstance(pp_dict, str):
                     pp_dict = pp_conf.get(pp_dict) or {"name": pp_dict}
diff --git a/test/test_config.py b/test/test_config.py
index bbe288ff..1d49d776 100644
--- a/test/test_config.py
+++ b/test/test_config.py
@@ -117,6 +117,24 @@ class TestConfig(unittest.TestCase):
         self.assertEqual(
             config.accumulate(("c", "c"), "l"), [5, 6])
 
+        config.set(()        , "l", 4)
+        config.set(("c",)    , "l", [2, 3])
+        config.set(("c", "c"), "l", 1)
+        self.assertEqual(
+            config.accumulate((), "l")        , [4])
+        self.assertEqual(
+            config.accumulate(("c",), "l")    , [2, 3, 4])
+        self.assertEqual(
+            config.accumulate(("c", "c"), "l"), [1, 2, 3, 4])
+
+        config.set(("c",), "l", None)
+        self.assertEqual(
+            config.accumulate((), "l")        , [4])
+        self.assertEqual(
+            config.accumulate(("c",), "l")    , [4])
+        self.assertEqual(
+            config.accumulate(("c", "c"), "l"), [1, 4])
+
     def test_set(self):
         config.set(()        , "c", [1, 2, 3])
         config.set(("b",)    , "c", [1, 2, 3])