diff --git a/beetsplug/substitute.py b/beetsplug/substitute.py
index 84eca9de1..d6476ae2f 100644
--- a/beetsplug/substitute.py
+++ b/beetsplug/substitute.py
@@ -35,7 +35,7 @@ class Substitute(BeetsPlugin):
         """Do the actual replacing."""
         if text:
             for pattern, replacement in self.substitute_rules:
-                new_text, subs_made = re.subn(pattern, replacement, text)
+                new_text, subs_made = pattern.subn(replacement, text)
                 if subs_made > 0:
                     return new_text
             return text
@@ -48,7 +48,7 @@ class Substitute(BeetsPlugin):
         Get the configuration, register template function and create list of
         substitute rules.
         """
-        super(Substitute, self).__init__()
+        super().__init__()
         self.substitute_rules = []
         self.template_funcs["substitute"] = self.tmpl_substitute
 
@@ -70,7 +70,7 @@ class Substitute(BeetsPlugin):
                     """
                 )
             )
-            pairs = [(key, view.as_str()) for key, view in self.config.items()]
+            pairs = self.config.flatten().items()
         else:
             pairs = self.config.as_pairs()
 
diff --git a/docs/plugins/substitute.rst b/docs/plugins/substitute.rst
index acd35226f..1ea4f8f55 100644
--- a/docs/plugins/substitute.rst
+++ b/docs/plugins/substitute.rst
@@ -13,6 +13,7 @@ Enable the ``substitute`` plugin (see :ref:`using-plugins`), then make a ``subst
 Each rule consists of a case-insensitive regular expression pattern, and a
 replacement string. For example, you might use:
 
+.. code-block:: yaml
     substitute:
       - .*jimi hendrix.*: Jimi Hendrix
 
@@ -22,6 +23,7 @@ multiple artists into the directory of the first artist. We can thus capture
 everything before the first ``,``, `` &`` or `` and``, and use this capture
 group in the output, discarding the rest of the string.
 
+.. code-block:: yaml
     substitute:
       - ^(.*?)(,| &| and).*: \1
 
@@ -34,5 +36,6 @@ This would handle all the below cases in a single rule:
 
 To apply the substitution, you have to call the function ``%substitute{}`` in the paths section. For example:
 
+.. code-block:: yaml
     paths:
-        default: %substitute{$albumartist}/$year - $album%aunique{}/$track - $title
\ No newline at end of file
+        default: %substitute{$albumartist}/$year - $album%aunique{}/$track - $title
diff --git a/test/plugins/test_substitute.py b/test/plugins/test_substitute.py
index 336edda9e..d193400d6 100644
--- a/test/plugins/test_substitute.py
+++ b/test/plugins/test_substitute.py
@@ -17,41 +17,42 @@
 from beets.test.helper import PluginTestCase, capture_log
 from beetsplug.substitute import Substitute
 
-PLUGIN_NAME = "substitute"
-
 
 class SubstitutePluginTest(PluginTestCase):
     plugin = "substitute"
     preload_plugin = False
 
+    def run_substitute(self, config, cases):
+        with self.configure_plugin(config):
+            for input, expected in cases:
+                assert Substitute().tmpl_substitute(input) == expected
+
     def test_simple_substitute(self):
-        with self.configure_plugin(
+        self.run_substitute(
             [
                 {"a": "b"},
                 {"b": "c"},
                 {"c": "d"},
-            ]
-        ):
-            cases = [("a", "b"), ("b", "c"), ("c", "d")]
-            for input, expected in cases:
-                assert Substitute().tmpl_substitute(input) == expected
+            ],
+            [("a", "b"), ("b", "c"), ("c", "d")],
+        )
 
     def test_case_insensitivity(self):
-        with self.configure_plugin([{"a": "b"}]):
-            assert Substitute().tmpl_substitute("A") == "b"
+        self.run_substitute([{"a": "b"}], [("A", "b")])
 
     def test_unmatched_input_preserved(self):
-        with self.configure_plugin([{"a": "b"}]):
-            assert Substitute().tmpl_substitute("c") == "c"
+        self.run_substitute([{"a": "b"}], [("c", "c")])
 
     def test_regex_to_static(self):
-        with self.configure_plugin([{".*jimi hendrix.*": "Jimi Hendrix"}]):
-            result = Substitute().tmpl_substitute("The Jimi Hendrix Experience")
-            assert result == "Jimi Hendrix"
+        self.run_substitute(
+            [{".*jimi hendrix.*": "Jimi Hendrix"}],
+            [("The Jimi Hendrix Experience", "Jimi Hendrix")],
+        )
 
     def test_regex_capture_group(self):
-        with self.configure_plugin([{"^(.*?)(,| &| and).*": r"\1"}]):
-            cases = [
+        self.run_substitute(
+            [{"^(.*?)(,| &| and).*": r"\1"}],
+            [
                 ("King Creosote & Jon Hopkins", "King Creosote"),
                 (
                     "Michael Hurley, The Holy Modal Rounders, Jeffrey Frederick & "
@@ -59,43 +60,33 @@ class SubstitutePluginTest(PluginTestCase):
                     "Michael Hurley",
                 ),
                 ("James Yorkston and the Athletes", "James Yorkston"),
-            ]
-            for input, expected in cases:
-                assert Substitute().tmpl_substitute(input) == expected
+            ],
+        )
 
     def test_partial_substitution(self):
-        with self.configure_plugin([{r"\.": ""}]):
-            cases = [
-                ("U.N.P.O.C.", "UNPOC"),
-            ]
-            for input, expected in cases:
-                assert Substitute().tmpl_substitute(input) == expected
+        self.run_substitute([{r"\.": ""}], [("U.N.P.O.C.", "UNPOC")])
 
     def test_break_on_first_match(self):
-        with self.configure_plugin(
+        self.run_substitute(
             [
                 {"a": "b"},
                 {"[ab]": "c"},
-            ]
-        ):
-            cases = [
+            ],
+            [
                 ("a", "b"),
                 ("b", "c"),
-            ]
-            for input, expected in cases:
-                assert Substitute().tmpl_substitute(input) == expected
+            ],
+        )
 
     def test_deprecated_config(self):
-        with self.configure_plugin(
+        self.run_substitute(
             {
                 "a": "b",
                 "b": "c",
                 "c": "d",
-            }
-        ):
-            cases = [("a", "b"), ("b", "c"), ("c", "d")]
-            for input, expected in cases:
-                assert Substitute().tmpl_substitute(input) == expected
+            },
+            [("a", "b"), ("b", "c"), ("c", "d")],
+        )
 
     def test_deprecated_config_warning(self):
         with capture_log() as logs: