diff --git a/src/device/usbd.c b/src/device/usbd.c
index 9c08a793..d4eccf0c 100644
--- a/src/device/usbd.c
+++ b/src/device/usbd.c
@@ -240,6 +240,9 @@ static void usbd_reset(uint8_t rhport)
  */
 void tud_task (void)
 {
+  // Skip if stack is not initialized
+  if ( !tusb_inited() ) return;
+
   // Loop until there is no more events in the queue
   while (1)
   {
diff --git a/src/host/usbh.c b/src/host/usbh.c
index 4334729e..a7e7c2ac 100644
--- a/src/host/usbh.c
+++ b/src/host/usbh.c
@@ -620,6 +620,9 @@ bool enum_task(hcd_event_t* event)
  */
 void tuh_task(void)
 {
+  // Skip if stack is not initialized
+  if ( !tusb_inited() ) return;
+
   // Loop until there is no more events in the queue
   while (1)
   {
diff --git a/src/tusb.c b/src/tusb.c
index ad2dcbfd..566d74df 100644
--- a/src/tusb.c
+++ b/src/tusb.c
@@ -68,6 +68,11 @@ bool tusb_init(void)
   return TUSB_ERROR_NONE;
 }
 
+bool tusb_inited(void)
+{
+  return _initialized;
+}
+
 /*------------------------------------------------------------------*/
 /* Debug
  *------------------------------------------------------------------*/
diff --git a/src/tusb.h b/src/tusb.h
index fb20c5ff..69c4d16d 100644
--- a/src/tusb.h
+++ b/src/tusb.h
@@ -108,6 +108,9 @@
 // Initialize device/host stack
 bool tusb_init(void);
 
+// Check if stack is initialized
+bool tusb_inited(void);
+
 // TODO
 // bool tusb_teardown(void);