diff --git a/index.html b/index.html
index 7ab17b1..556811a 100644
--- a/index.html
+++ b/index.html
@@ -482,10 +482,11 @@
                                     <label
                                         for="nogoFile"
                                         data-i18n="loadNogos.file"
-                                        >File:
+                                        >File (.geojson):
                                     </label>
                                     <input
                                         type="file"
+                                        accept=".geojson"
                                         name="nogoFile"
                                         id="nogoFile"
                                     />
diff --git a/locales/en.json b/locales/en.json
index e391b6e..a852873 100644
--- a/locales/en.json
+++ b/locales/en.json
@@ -61,7 +61,7 @@
   },
   "loadNogos": {
     "defaultProperties": "Default properties",
-    "file": "File: ",
+    "file": "File (.geojson): ",
     "load": "Load",
     "nogoBuffer": "Buffer no-go areas (in meters): ",
     "nogoRadius": "No-go radius (for points): ",