diff --git a/swh/loader/svn/tests/test_utils.py b/swh/loader/svn/tests/test_utils.py
--- a/swh/loader/svn/tests/test_utils.py
+++ b/swh/loader/svn/tests/test_utils.py
@@ -285,6 +285,17 @@
                 True,
             ),
         ),
+        (
+            "^/../../skin-maker@21 third-party/skins/toolkit",
+            "trunk/externals",
+            "http://svn.example.org/repos/test",
+            (
+                "third-party/skins/toolkit",
+                "http://svn.example.org/skin-maker",
+                21,
+                True,
+            ),
+        ),
         (
             "../skins skins",
             "trunk/externals",
diff --git a/swh/loader/svn/utils.py b/swh/loader/svn/utils.py
--- a/swh/loader/svn/utils.py
+++ b/swh/loader/svn/utils.py
@@ -235,6 +235,7 @@
             # URL relative to the root of the repository in which the svn:externals
             # property is versioned
             external_url = svn_urljoin(repo_url, external_part[2:])
+            relative_url = not external_url.startswith(repo_url)
         elif external_part.startswith("//"):
             # URL relative to the scheme of the URL of the directory on which the
             # svn:externals property is set