diff --git a/backend/web.py b/backend/web.py
index d1d8626b54ec6436542b29e585496bf093a946c2..a63ab305fb7a8a27263072932049e13e00f3a308 100644
--- a/backend/web.py
+++ b/backend/web.py
@@ -22,7 +22,7 @@ class SSLHandler:
         else:
             pem_cert = ssl.get_server_certificate((self.host, self.port), timeout=5)
             cert = x509.load_pem_x509_certificate(pem_cert.encode())
-            not_after = cert.not_valid_after.timestamp()
+            not_after = cert.not_valid_after_utc.timestamp()
             return tls_utils.get_expiry_timestamps(not_after)[1]
 
 class SSLVerificator: