diff --git a/python/mozbuild/mozbuild/vendor/vendor_python.py b/python/mozbuild/mozbuild/vendor/vendor_python.py
index db554e..a4d003 100644
--- a/python/mozbuild/mozbuild/vendor/vendor_python.py
+++ b/python/mozbuild/mozbuild/vendor/vendor_python.py
@@ -34,6 +34,10 @@
     # modified 'dummy' version of it so that the dependency checks still succeed, but
     # if it ever is attempted to be used, it will fail gracefully.
     "ansicon",
+    # jsonschema 4.17.3 is incompatible with Python 3.14+,
+    # but later versions use a dependency with Rust components, which we thus can't vendor.
+    # For now we apply the minimal patch to jsonschema to make it work again.
+    "jsonschema",
 }
 
 
diff --git a/third_party/python/jsonschema/jsonschema/validators.py b/third_party/python/jsonschema/jsonschema/validators.py
index 66e803..88316a 100644
--- a/third_party/python/jsonschema/jsonschema/validators.py
+++ b/third_party/python/jsonschema/jsonschema/validators.py
@@ -875,8 +875,11 @@ def _find_in_subschemas(self, url):
             return None
         uri, fragment = urldefrag(url)
         for subschema in subschemas:
+            id = subschema["$id"]
+            if not isinstance(id, str):
+                continue
             target_uri = self._urljoin_cache(
-                self.resolution_scope, subschema["$id"],
+                self.resolution_scope, id,
             )
             if target_uri.rstrip("/") == uri.rstrip("/"):
                 if fragment: