diff --git a/otherlibs/stdune/src/path.ml b/otherlibs/stdune/src/path.ml
index fc0bf432045..8a983b76b07 100644
--- a/otherlibs/stdune/src/path.ml
+++ b/otherlibs/stdune/src/path.ml
@@ -570,6 +570,7 @@ let is_descendant t ~of_ =
   match t, of_ with
   | In_source_tree t, In_source_tree of_ -> Source0.is_descendant t ~of_
   | In_build_dir t, In_build_dir of_ -> Build.is_descendant t ~of_
+  | External t, External of_ -> External.is_descendant t ~of_
   | _ -> false
 ;;
 
diff --git a/otherlibs/stdune/src/path_external.ml b/otherlibs/stdune/src/path_external.ml
index d97509a15e6..97e75848dd4 100644
--- a/otherlibs/stdune/src/path_external.ml
+++ b/otherlibs/stdune/src/path_external.ml
@@ -75,7 +75,7 @@ include (
 let to_string_maybe_quoted t = String.maybe_quoted (to_string t)
 
 let is_descendant b ~of_:a =
-  is_root a || String.starts_with ~prefix:(to_string a ^ "/") (to_string b)
+  is_root a || equal a b || String.starts_with ~prefix:(to_string a ^ "/") (to_string b)
 ;;
 
 module Map = String.Map
diff --git a/otherlibs/stdune/test/path_tests.ml b/otherlibs/stdune/test/path_tests.ml
index 8352cfd6713..018cc99686c 100644
--- a/otherlibs/stdune/test/path_tests.ml
+++ b/otherlibs/stdune/test/path_tests.ml
@@ -129,18 +129,12 @@ true
 
 let%expect_test _ =
   is_descendant (e "/foo/bar") ~of_:(e "/foo");
-  [%expect
-    {|
-false
-|}]
+  [%expect {| true |}]
 ;;
 
 let%expect_test _ =
   is_descendant (e "/foo/bar") ~of_:(e "/foo/bar");
-  [%expect
-    {|
-false
-|}]
+  [%expect {| true |}]
 ;;
 
 let%expect_test _ =
@@ -153,18 +147,12 @@ false
 
 let%expect_test _ =
   is_descendant (e "/foo/bar/") ~of_:(e "/foo/bar");
-  [%expect
-    {|
-false
-|}]
+  [%expect {| true |}]
 ;;
 
 let%expect_test _ =
   is_descendant (e "/foo/bar") ~of_:(e "/");
-  [%expect
-    {|
-false
-|}]
+  [%expect {| true |}]
 ;;
 
 let%expect_test _ =