diff --git a/openml/_api_calls.py b/openml/_api_calls.py
index 81296b3da..7bac3aebb 100644
--- a/openml/_api_calls.py
+++ b/openml/_api_calls.py
@@ -363,6 +363,11 @@ def _send_request(  # noqa: C901, PLR0912
     files: FILE_ELEMENTS_TYPE | None = None,
     md5_checksum: str | None = None,
 ) -> requests.Response:
+    MAX_URL_LENGTH = 2000  # Conservative limit for broad compatibility
+
+    if len(url) > MAX_URL_LENGTH:
+        raise OpenMLServerError("URI too long!")
+
     n_retries = max(1, config.connection_n_retries)
 
     response: requests.Response | None = None
diff --git a/tests/files/misc/features_with_whitespaces.xml.pkl b/tests/files/misc/features_with_whitespaces.xml.pkl
new file mode 100644
index 000000000..f6a775cc7
Binary files /dev/null and b/tests/files/misc/features_with_whitespaces.xml.pkl differ