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 0d7525a0..974d8bf7 100644
--- a/test/unit-tests/path.mlt
+++ b/test/unit-tests/path.mlt
@@ -37,17 +37,17 @@ Path.(is_descendant (r "foo/") ~of_:(r "foo"))
 
 Path.(is_descendant (r "foo") ~of_:(r "bar"))
 [%%expect{|
-Exception: Invalid_argument "index out of bounds".
+- : bool = false
 |}]
 
 Path.(is_descendant (r "foo") ~of_:(r "bar/"))
 [%%expect{|
-Exception: Invalid_argument "index out of bounds".
+- : bool = false
 |}]
 
 Path.(is_descendant (r "foo/") ~of_:(r "bar"))
 [%%expect{|
-Exception: Invalid_argument "index out of bounds".
+- : bool = false
 |}]
 
 Path.(is_descendant (r "glob/foo") ~of_:(r "glob"))