diff --git a/.travis.yml b/.travis.yml
index 0927f434b5..7b18fcd107 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -5,6 +5,7 @@ notifications:
 
 before_script:
 # travis has changed to 64-bit and we require 32-bit compatibility libraries
+  - sudo apt-get update
   - "sudo apt-get -qq install libc6:i386 libgcc1:i386 gcc-4.6-base:i386 libstdc++5:i386 libstdc++6:i386 || true"
   - "[ $RTT_TOOL_CHAIN = 'sourcery-arm' ] && curl -s https://sourcery.mentor.com/public/gnu_toolchain/arm-none-eabi/arm-2012.09-63-arm-none-eabi-i686-pc-linux-gnu.tar.bz2 | sudo tar xjf - -C /opt && export RTT_EXEC_PATH=/opt/arm-2012.09/bin && /opt/arm-2012.09/bin/arm-none-eabi-gcc --version || true"
   - "[ $RTT_TOOL_CHAIN = 'sourcery-mips' ] && curl -s https://sourcery.mentor.com/public/gnu_toolchain/mips-sde-elf/mips-2012.09-98-mips-sde-elf-i686-pc-linux-gnu.tar.bz2 | sudo tar xjf - -C /opt && export RTT_EXEC_PATH=/opt/mips-2012.09/bin && /opt/mips-2012.09/bin/mips-sde-elf-gcc --version || true"
diff --git a/README.md b/README.md
index 754f6995e7..8c58a9efd7 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
-RT-Thread
-=========
+# RT-Thread #
 
 [![Build Status](https://travis-ci.org/RT-Thread/rt-thread.png)](https://travis-ci.org/RT-Thread/rt-thread)
 
 RT-Thread is an open source real-time operating system for embedded devices.
+
diff --git a/components/drivers/usb/usbdevice/core/core.c b/components/drivers/usb/usbdevice/core/core.c
index c79820642a..2f4a21eee4 100644
--- a/components/drivers/usb/usbdevice/core/core.c
+++ b/components/drivers/usb/usbdevice/core/core.c
@@ -1237,7 +1237,6 @@ rt_err_t rt_usbd_set_altsetting(uintf_t intf, rt_uint8_t value)
 
     /* parameter check */
     RT_ASSERT(intf != RT_NULL);
-    RT_ASSERT(setting != RT_NULL);
 
     /* find an alternate setting */
     setting = rt_usbd_find_altsetting(intf, value);
@@ -1308,6 +1307,12 @@ static void rt_usbd_thread_entry(void* parameter)
                 rt_kprintf("invalid usb device\n");
             break;
         case USB_MSG_DATA_NOTIFY:
+            device = rt_usbd_find_device(msg.dcd);
+            if(device == RT_NULL)
+            {
+                rt_kprintf("invalid usb device\n");
+                break;
+            }
             ep = rt_usbd_find_endpoint(device, &cls, msg.content.ep_msg.ep_addr);
             if(ep != RT_NULL)
                 ep->handler(device, cls, msg.content.ep_msg.size);