diff --git a/src/stdune/path.ml b/src/stdune/path.ml
index d30e23e3..ec8fd4ad 100644
--- a/src/stdune/path.ml
+++ b/src/stdune/path.ml
@@ -206,7 +206,7 @@ module Local = struct
       let of_len = String.length of_ in
       let t_len = String.length t in
       (t_len = of_len && t = of_) ||
-      (t_len >= of_len && t.[of_len] = '/' && String.is_prefix t ~prefix:of_)
+      (t_len > of_len && t.[of_len] = '/' && String.is_prefix t ~prefix:of_)
 
   let reach t ~from =
     let rec loop t from =
diff --git a/test/unit-tests/path.mlt b/test/unit-tests/path.mlt
index 3392b32b..974d8bf7 100644
--- a/test/unit-tests/path.mlt
+++ b/test/unit-tests/path.mlt
@@ -20,6 +20,71 @@ Path.(descendant (relative root "foo") ~of_:(relative root "bar"))
 - : Stdune.Path.t option = None
 |}]
 
+Path.(is_descendant (r "foo") ~of_:(r "foo"))
+[%%expect{|
+- : bool = true
+|}]
+
+Path.(is_descendant (r "foo") ~of_:(r "foo/"))
+[%%expect{|
+- : bool = true
+|}]
+
+Path.(is_descendant (r "foo/") ~of_:(r "foo"))
+[%%expect{|
+- : bool = true
+|}]
+
+Path.(is_descendant (r "foo") ~of_:(r "bar"))
+[%%expect{|
+- : bool = false
+|}]
+
+Path.(is_descendant (r "foo") ~of_:(r "bar/"))
+[%%expect{|
+- : bool = false
+|}]
+
+Path.(is_descendant (r "foo/") ~of_:(r "bar"))
+[%%expect{|
+- : bool = false
+|}]
+
+Path.(is_descendant (r "glob/foo") ~of_:(r "glob"))
+[%%expect{|
+- : bool = true
+|}]
+
+Path.(is_descendant (r "glob/foo") ~of_:(r "glob/"))
+[%%expect{|
+- : bool = true
+|}]
+
+Path.(is_descendant (Path.absolute "/foo/bar") ~of_:(Path.absolute "/foo"))
+[%%expect{|
+- : bool = false
+|}]
+
+Path.(is_descendant (Path.absolute "/foo/bar") ~of_:(Path.absolute "/foo/bar"))
+[%%expect{|
+- : bool = false
+|}]
+
+Path.(is_descendant (Path.absolute "/foo/bar") ~of_:(Path.absolute "/foo/bar/"))
+[%%expect{|
+- : bool = false
+|}]
+
+Path.(is_descendant (Path.absolute "/foo/bar/") ~of_:(Path.absolute "/foo/bar"))
+[%%expect{|
+- : bool = false
+|}]
+
+Path.(is_descendant (Path.absolute "/foo/bar") ~of_:(Path.absolute "/"))
+[%%expect{|
+- : bool = false
+|}]
+
 Path.(descendant (r "foo") ~of_:(r "foo/"))
 [%%expect{|
 - : Stdune.Path.t option = Some foo