diff --git a/weasyprint/css/__init__.py b/weasyprint/css/__init__.py
index 914f345eb..a6d7e443a 100644
--- a/weasyprint/css/__init__.py
+++ b/weasyprint/css/__init__.py
@@ -26,7 +26,7 @@
from ..urls import URLFetchingError, get_url_attribute, url_join
from . import computed_values, counters, media_queries
from .properties import INHERITED, INITIAL_NOT_COMPUTED, INITIAL_VALUES
-from .utils import remove_whitespace
+from .utils import get_url, remove_whitespace
from .validation import preprocess_declarations
from .validation.descriptors import preprocess_descriptors
@@ -838,9 +838,15 @@ def preprocess_stylesheet(device_media_type, base_url, stylesheet_rules,
continue
tokens = remove_whitespace(rule.prelude)
- if tokens and tokens[0].type in ('url', 'string'):
- url = tokens[0].value
- else:
+ url = None
+ if tokens and len(tokens) == 1:
+ if tokens[0].type == 'string':
+ url = tokens[0].value
+ else:
+ url_tuple = get_url(tokens[0], base_url)
+ if url_tuple and url_tuple[1][0] == 'external':
+ url = url_tuple[1][1]
+ if url is None:
continue
media = media_queries.parse_media_query(tokens[1:])
if media is None:
diff --git a/weasyprint/tests/test_api.py b/weasyprint/tests/test_api.py
index ed659d6a1..24ce74554 100644
--- a/weasyprint/tests/test_api.py
+++ b/weasyprint/tests/test_api.py
@@ -899,6 +899,8 @@ def test(html, blank=False):
'url(weasyprint-custom:foo/é_%e9_pattern)">')
test('')
test('')
+ test('')
+ test('')
test('')
with capture_logs() as logs: