diff --git a/CHANGES.md b/CHANGES.md
index 8790263aa7d..aa709fa461c 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -6,6 +6,8 @@
 
 - Add new `--workers` parameter (#2514)
 - Bumped typed-ast version minimum to 1.4.3 for 3.10 compatibility (#2519)
+- Fixed feature detection for positional-only arguments in lambdas (#2532)
+- Bumped typed-ast version minimum to 1.4.3 for 3.10 compatiblity (#2519)
 - Allow specifying `config` in config files (#2525)
 
 ### _Blackd_
diff --git a/docs/requirements.txt b/docs/requirements.txt
index 4c5b700412a..296efc5cc84 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -1,6 +1,6 @@
 # Used by ReadTheDocs; pinned requirements for stability.
 
 myst-parser==0.15.1
-Sphinx==4.1.2
+Sphinx==4.2.0
 sphinxcontrib-programoutput==0.17
 sphinx_copybutton==0.4.0
diff --git a/src/black/__init__.py b/src/black/__init__.py
index b8c086ad9a1..21b966113ef 100644
--- a/src/black/__init__.py
+++ b/src/black/__init__.py
@@ -1125,7 +1125,11 @@ def get_features_used(node: Node) -> Set[Feature]:
                 features.add(Feature.NUMERIC_UNDERSCORES)
 
         elif n.type == token.SLASH:
-            if n.parent and n.parent.type in {syms.typedargslist, syms.arglist}:
+            if n.parent and n.parent.type in {
+                syms.typedargslist,
+                syms.arglist,
+                syms.varargslist,
+            }:
                 features.add(Feature.POS_ONLY_ARGUMENTS)
 
         elif n.type == token.COLONEQUAL:
diff --git a/tests/test_black.py b/tests/test_black.py
index b672425bba8..4fb2423593a 100644
--- a/tests/test_black.py
+++ b/tests/test_black.py
@@ -805,6 +805,10 @@ def test_get_features_used(self) -> None:
         self.assertEqual(black.get_features_used(node), set())
         node = black.lib2to3_parse(expected)
         self.assertEqual(black.get_features_used(node), set())
+        node = black.lib2to3_parse("lambda a, /, b: ...")
+        self.assertEqual(black.get_features_used(node), {Feature.POS_ONLY_ARGUMENTS})
+        node = black.lib2to3_parse("def fn(a, /, b): ...")
+        self.assertEqual(black.get_features_used(node), {Feature.POS_ONLY_ARGUMENTS})
 
     def test_get_future_imports(self) -> None:
         node = black.lib2to3_parse("\n")