diff --git a/extmod/modtrezorconfig/norcow_config.h b/extmod/modtrezorconfig/norcow_config.h
index dd08076802..74e19ffc45 100644
--- a/extmod/modtrezorconfig/norcow_config.h
+++ b/extmod/modtrezorconfig/norcow_config.h
@@ -2,9 +2,3 @@
 #define NORCOW_UNIX 1
 #define NORCOW_FILE "/var/tmp/trezor.config"
 #endif
-
-#ifdef STM32_HAL_H
-// TODO: switch to native implementation when finished
-#define NORCOW_UNIX 1
-#define NORCOW_FILE "/sd/trezor.config"
-#endif
diff --git a/src/trezor/config.py b/src/trezor/config.py
index 471f64435e..1db7ad0593 100644
--- a/src/trezor/config.py
+++ b/src/trezor/config.py
@@ -1,6 +1,10 @@
-from TrezorConfig import Config
-
-_config = Config()
+import sys
+if sys.platform in ['trezor', 'pyboard']:  # stmhal
+    from config_mock import Config
+    _config = Config('/sd/trezor.config')
+else:
+    from TrezorConfig import Config
+    _config = Config()
 
 def get(app, key, default=None):
     v = _config.get(app, key)
diff --git a/src/trezor/config_mock.py b/src/trezor/config_mock.py
new file mode 100644
index 0000000000..06b32891c7
--- /dev/null
+++ b/src/trezor/config_mock.py
@@ -0,0 +1,37 @@
+# mock implementation using binary file
+
+import ustruct
+
+def Config():
+
+    def __init__(self, filename):
+        self._data = {}
+        self._file = filename
+        try:
+            with open(self._file, 'rb') as f:
+                while True:
+                    d = f.read(4)
+                    if len(d) != 4:
+                        break
+                    k, l = ustruct.unpack('<HH', d)
+                    v = f.read(l)
+                    self._data[k] = v
+        except OSError:
+            pass
+
+    def _save(self):
+        with open(self._file, 'wb') as f:
+        for k, v in self._data.items():
+            f.write(ustruct.pack('<HH', k, len(v)))
+            f.write(v)
+
+    def get(self, app_id, key, default=None):
+        return self._data.get((app_id << 8) | key, default)
+
+    def set(self, app_id, key, value):
+        self._data[(app_id << 8) | key] = value
+        self._save()
+
+    def wipe(self):
+        self._data = {}
+        self._save()
diff --git a/vendor/norcow b/vendor/norcow
index 934b3cd1fb..5543b20345 160000
--- a/vendor/norcow
+++ b/vendor/norcow
@@ -1 +1 @@
-Subproject commit 934b3cd1fbef79fd6b079b787e6e3225bbe5684c
+Subproject commit 5543b20345cfd2f8e4660c04bd8c5e588c9b9dd6