diff --git a/boot/mynewt/src/main.c b/boot/mynewt/src/main.c
index 384567b..63a274b 100755
--- a/boot/mynewt/src/main.c
+++ b/boot/mynewt/src/main.c
@@ -67,9 +67,9 @@
     int rc;
 
     hal_bsp_init();
-    os_dev_initialize_all(OS_DEV_INIT_PRIMARY);
-    os_dev_initialize_all(OS_DEV_INIT_SECONDARY);
 #ifdef MCUBOOT_SERIAL
+    /* initialize uart without os */
+    os_dev_initialize_all(OS_DEV_INIT_PRIMARY);
     sysinit();
 #else
     flash_map_init();