diff --git a/httpretty/core.py b/httpretty/core.py
index 683c364..5e42c49 100644
--- a/httpretty/core.py
+++ b/httpretty/core.py
@@ -843,6 +843,8 @@ class httpretty(HttpBaseClass):
 
     @classmethod
     def reset(cls):
+        global POTENTIAL_HTTP_PORTS
+        POTENTIAL_HTTP_PORTS = set([80, 443])
         cls._entries.clear()
         cls.latest_requests = []
         cls.last_request = HTTPrettyRequestEmpty()