diff --git a/src/pretix/presale/style.py b/src/pretix/presale/style.py
index 065420259..cbb110d4f 100644
--- a/src/pretix/presale/style.py
+++ b/src/pretix/presale/style.py
@@ -20,10 +20,10 @@ def regenerate_css(event_id: int):
     event = Event.objects.select_related('organizer').get(pk=event_id)
     sassdir = os.path.join(settings.STATIC_ROOT, 'pretixpresale/scss')
 
-    sassrules = [
-        '$brand-primary: {};'.format(event.settings.get('primary_color')),
-        '@import "main.scss";',
-    ]
+    sassrules = []
+    if event.settings.get('primary_color'):
+        sassrules.append('$brand-primary: {};'.format(event.settings.get('primary_color')))
+    sassrules.append('@import "main.scss";')
 
     css = sass.compile(
         string="\n".join(sassrules),