diff --git a/src/waitress/task.py b/src/waitress/task.py
index f24fbe00..cb821e00 100644
--- a/src/waitress/task.py
+++ b/src/waitress/task.py
@@ -557,7 +557,7 @@ def get_environment(self):
         }
 
         for key, value in dict(request.headers).items():
-            value = value.strip()
+            value = value.strip(" \t")
             mykey = rename_headers.get(key, None)
             if mykey is None:
                 mykey = "HTTP_" + key