diff --git a/manifest.json b/manifest.json
index fc04348..ee5e1e9 100644
--- a/manifest.json
+++ b/manifest.json
@@ -8,7 +8,9 @@
     "128": "icons/icon128.png"
   },
   "permissions": [
-    "https://www.strava.com/*"
+    "declarativeNetRequestWithHostAccess",
+    "https://www.strava.com/*",
+    "https://mapserver.mapy.cz/*"
   ],
   "content_scripts": [
     {
@@ -20,6 +22,15 @@
       ]
     }
   ],
+  "declarative_net_request": {
+    "rule_resources": [
+      {
+        "id": "mapy_cz",
+        "enabled": true,
+        "path": "rules_mapy_cz.json"
+      }
+    ]
+  },
   "web_accessible_resources": [
     "3rd/Leaflet.GoogleMutant.js",
     "3rd/jquery-3.5.1.min.js",
diff --git a/rules_mapy_cz.json b/rules_mapy_cz.json
new file mode 100644
index 0000000..67756dc
--- /dev/null
+++ b/rules_mapy_cz.json
@@ -0,0 +1,24 @@
+[
+  {
+    "id": 1,
+    "priority": 1,
+    "action": {
+      "type": "modifyHeaders",
+      "requestHeaders": [
+        {
+          "header": "referer",
+          "operation": "set",
+          "value": "https://mapy.cz/"
+        },
+        {
+          "header": "origin",
+          "operation": "remove"
+        }
+      ]
+    },
+    "condition": {
+      "initiatorDomains": ["www.strava.com"],
+      "urlFilter": "||mapserver.mapy.cz/*/*-*-*"
+    }
+  }
+]