diff --git a/gallery_dl/config.py b/gallery_dl/config.py
index 53036169..a3c71cde 100644
--- a/gallery_dl/config.py
+++ b/gallery_dl/config.py
@@ -108,6 +108,38 @@ def interpolate(path, key, default=None, *, conf=_config):
     return default
 
 
+def interpolate_common(common, paths, key, default=None, *, conf=_config):
+    """Interpolate the value of 'key'
+    using multiple 'paths' along a 'common' ancestor
+    """
+    if key in conf:
+        return conf[key]
+
+    # follow the common path
+    try:
+        for p in common:
+            conf = conf[p]
+            if key in conf:
+                default = conf[key]
+    except Exception:
+        return default
+
+    # try all paths until a value is found
+    value = util.SENTINEL
+    for path in paths:
+        c = conf
+        try:
+            for p in path:
+                c = c[p]
+                if key in c:
+                    value = c[key]
+        except Exception:
+            pass
+        if value is not util.SENTINEL:
+            return value
+    return default
+
+
 def set(path, key, value, *, conf=_config):
     """Set the value of property 'key' for this session"""
     for p in path:
diff --git a/gallery_dl/extractor/common.py b/gallery_dl/extractor/common.py
index 4d314c23..bbbd8a65 100644
--- a/gallery_dl/extractor/common.py
+++ b/gallery_dl/extractor/common.py
@@ -492,10 +492,13 @@ class SharedConfigMixin():
     """Enable sharing of config settings based on 'basecategory'"""
     basecategory = ""
 
-    def config(self, key, default=None, *, sentinel=util.SENTINEL):
-        value = Extractor.config(self, key, sentinel)
-        return value if value is not sentinel else config.interpolate(
-            ("extractor", self.basecategory, self.subcategory), key, default)
+    def config(self, key, default=None):
+        return config.interpolate_common(
+            ("extractor",), (
+                (self.category, self.subcategory),
+                (self.basecategory, self.subcategory),
+            ), key, default,
+        )
 
 
 def generate_extractors(extractor_data, symtable, classes):
diff --git a/gallery_dl/extractor/mastodon.py b/gallery_dl/extractor/mastodon.py
index f5e502b6..fa1fecc6 100644
--- a/gallery_dl/extractor/mastodon.py
+++ b/gallery_dl/extractor/mastodon.py
@@ -27,11 +27,12 @@ class MastodonExtractor(Extractor):
         Extractor.__init__(self, match)
         self.api = MastodonAPI(self)
 
-    def config(self, key, default=None, *, sentinel=util.SENTINEL):
-        value = Extractor.config(self, key, sentinel)
-        return value if value is not sentinel else config.interpolate(
-            ("extractor", "mastodon", self.instance, self.subcategory),
-            key, default,
+    def config(self, key, default=None):
+        return config.interpolate_common(
+            ("extractor",), (
+                (self.category, self.subcategory),
+                (self.basecategory, self.instance, self.subcategory),
+            ), key, default,
         )
 
     def items(self):
diff --git a/test/test_config.py b/test/test_config.py
index 4171435f..a9cefd40 100644
--- a/test/test_config.py
+++ b/test/test_config.py
@@ -68,6 +68,34 @@ class TestConfig(unittest.TestCase):
         self.assertEqual(config.interpolate(("b",), "d", 1) , 2)
         self.assertEqual(config.interpolate(("d",), "d", 1) , 2)
 
+    def test_interpolate_common(self):
+
+        def lookup():
+            return config.interpolate_common(
+                ("Z1", "Z2"), (
+                    ("A1", "A2"),
+                    ("B1",),
+                    ("C1", "C2", "C3"),
+                ), "KEY", "DEFAULT",
+            )
+
+        def test(path, value, expected=None):
+            config.set(path, "KEY", value)
+            self.assertEqual(lookup(), expected or value)
+
+        self.assertEqual(lookup(), "DEFAULT")
+        test(("Z1",), 1)
+        test(("Z1", "Z2"), 2)
+        test(("Z1", "Z2", "C1"), 3)
+        test(("Z1", "Z2", "C1", "C2"), 4)
+        test(("Z1", "Z2", "C1", "C2", "C3"), 5)
+        test(("Z1", "Z2", "B1"), 6)
+        test(("Z1", "Z2", "A1"), 7)
+        test(("Z1", "Z2", "A1", "A2"), 8)
+        test(("Z1", "A1", "A2"), 999, 8)
+        test(("Z1", "Z2", "A1", "A2", "A3"), 999, 8)
+        test((), 9)
+
     def test_set(self):
         config.set(()        , "c", [1, 2, 3])
         config.set(("b",)    , "c", [1, 2, 3])