diff --git a/spiderweb/middleware/gzip.py b/spiderweb/middleware/gzip.py
index cdf55a1..1f956a1 100644
--- a/spiderweb/middleware/gzip.py
+++ b/spiderweb/middleware/gzip.py
@@ -1,36 +1,36 @@
-
 """
-    Source code inspiration :https://github.com/colour-science/flask-compress/blob/master/flask_compress/flask_compress.py
+Source code inspiration: https://github.com/colour-science/flask-compress/blob/master/flask_compress/flask_compress.py
 """
 
-
 from spiderweb.middleware import SpiderwebMiddleware
 from spiderweb.request import Request
 from spiderweb.response import HttpResponse
 
-
 import gzip
 
 
 class GzipMiddleware(SpiderwebMiddleware):
-    
+
     algorithm = "gzip"
     minimum_length = 500
 
-    def post_process(self, request: Request, response: HttpResponse, rendered_response: str) -> str:
-        
-        #right status, length > 500, instance string (because FileResponse returns list of bytes ,
+    def post_process(
+        self, request: Request, response: HttpResponse, rendered_response: str
+    ) -> str:
+
+        # right status, length > 500, instance string (because FileResponse returns list of bytes,
         # not already compressed, and client accepts gzip
-        if not (200 <= response.status_code < 300) or \
-           len(rendered_response) < self.minimum_length or \
-           not isinstance(rendered_response, str) or \
-           self.algorithm in response.headers.get("Content-Encoding", "") or \
-           self.algorithm not in request.headers.get("Accept-Encoding", ""):
-           return rendered_response
-        
-        zipped = gzip.compress(rendered_response.encode('UTF-8'))
+        if (
+            not (200 <= response.status_code < 300)
+            or len(rendered_response) < self.minimum_length
+            or not isinstance(rendered_response, str)
+            or self.algorithm in response.headers.get("Content-Encoding", "")
+            or self.algorithm not in request.headers.get("Accept-Encoding", "")
+        ):
+            return rendered_response
+
+        zipped = gzip.compress(rendered_response.encode("UTF-8"), compresslevel=6)
         response.headers["Content-Encoding"] = self.algorithm
         response.headers["Content-Length"] = str(len(zipped))
-        
-        return zipped   
-        
+
+        return zipped.decode("UTF-8")