diff --git a/gcn_email/core.py b/gcn_email/core.py
index 2d6aa25..5d3d03b 100644
--- a/gcn_email/core.py
+++ b/gcn_email/core.py
@@ -20,7 +20,7 @@
 from .helpers import periodic_task
 
 SESV2 = boto3.client("sesv2")
-SENDER = f'GCN Notices <{os.environ["EMAIL_SENDER"]}>'
+SENDER = f"GCN Notices <{os.environ['EMAIL_SENDER']}>"
 
 # Maximum send rate
 MAX_SENDS = boto3.client("ses").get_send_quota()["MaxSendRate"]