diff --git a/readthedocs/core/resolver.py b/readthedocs/core/resolver.py
index abe1d5d9671..46ebff2d16a 100644
--- a/readthedocs/core/resolver.py
+++ b/readthedocs/core/resolver.py
@@ -161,10 +161,13 @@ def resolve(self, project, require_https_domain=False, filename='', private=None
             domain = getattr(settings, 'PRODUCTION_DOMAIN')
 
         protocol = 'http'
-        if custom_domain:
-            # Rely on the ``Domain.https`` field or force it if specified
-            if custom_domain.https or require_https_domain:
-                protocol = 'https'
+        # Rely on the ``Domain.https`` field or force it if specified
+        use_https_protocol = any([
+            (custom_domain and custom_domain.https),
+            require_https_domain,
+        ])
+        if use_https_protocol:
+            protocol = 'https'
         else:
             # Use HTTPS if settings specify
             public_domain = getattr(settings, 'PUBLIC_DOMAIN', None)