diff --git a/apps/sokoban/Microban.txt b/apps/sokoban/Microban.sok
similarity index 100%
rename from apps/sokoban/Microban.txt
rename to apps/sokoban/Microban.sok
diff --git a/apps/sokoban/app.js b/apps/sokoban/app.js
index 90b24ed11..b7d89d6ba 100644
--- a/apps/sokoban/app.js
+++ b/apps/sokoban/app.js
@@ -61,9 +61,9 @@ function next_map_offsets(filename, start_offset) {
 
 let config = s.readJSON("sokoban.json", true);
 if (config === undefined) {
-    let initial_offsets = next_map_offsets("Microban.txt", 0);
+    let initial_offsets = next_map_offsets("Microban.sok", 0);
     config = {
-        levels_sets: ["Microban.txt"], // all known files containing levels
+        levels_sets: ["Microban.sok"], // all known files containing levels
         levels_set: 0, // which set are we using ?
         current_maps: [0], // what is current map on each set ?
         offsets: [initial_offsets], // known offsets for each levels set (binary positions of maps in each file)
@@ -461,4 +461,4 @@ Bangle.setLocked(false);
 
 current_map = config.current_map;
 offsets = config.offsets;
-load_current_map();
\ No newline at end of file
+load_current_map();
diff --git a/apps/sokoban/metadata.json b/apps/sokoban/metadata.json
index 191cea1e0..7a4d5bc50 100644
--- a/apps/sokoban/metadata.json
+++ b/apps/sokoban/metadata.json
@@ -13,7 +13,7 @@
   "readme": "README.md",
   "storage": [
     {"name":"sokoban.app.js","url":"app.js"},
-    {"name":"Microban.txt", "url":"Microban.txt"},
+    {"name":"Microban.sok", "url":"Microban.sok"},
     {"name":"sokoban.img","url":"app-icon.js","evaluate":true}
   ],
   "data": [{"name":"sokoban.json"}