diff --git a/src/samd21/main.c b/src/samd21/main.c
index a9da6324..4687fc34 100644
--- a/src/samd21/main.c
+++ b/src/samd21/main.c
@@ -11,6 +11,26 @@
 DECL_CONSTANT(MCU, "samd21g");
 
 
+/****************************************************************
+ * watchdog handler
+ ****************************************************************/
+
+void
+watchdog_reset(void)
+{
+    WDT->CLEAR.reg = 0xa5;
+}
+DECL_TASK(watchdog_reset);
+
+void
+watchdog_init(void)
+{
+    WDT->CONFIG.reg = WDT_CONFIG_PER_16K; // 500ms timeout
+    WDT->CTRL.reg = WDT_CTRL_ENABLE;
+}
+DECL_INIT(watchdog_init);
+
+
 /****************************************************************
  * misc functions
  ****************************************************************/