diff --git a/fs_mgr/tests/adb-remount-test.sh b/fs_mgr/tests/adb-remount-test.sh
index 5827b1d..ed55768 100755
--- a/fs_mgr/tests/adb-remount-test.sh
+++ b/fs_mgr/tests/adb-remount-test.sh
@@ -219,13 +219,31 @@
   echo ${hours}:`expr ${minutes} / 10``expr ${minutes} % 10`:`expr ${seconds} / 10``expr ${seconds} % 10`
 }
 
+[ "USAGE: USB_DEVICE=\`usb_devnum [--next]\`
+
+USB_DEVICE contains cache. Update if system changes.
+
+Returns: the devnum for the USB_SERIAL device" ]
+usb_devnum() {
+  if [ -n "${USB_SERIAL}" ]; then
+    local usb_device=`cat ${USB_SERIAL%/serial}/devnum 2>/dev/null | tr -d ' \t\r\n'`
+    if [ -n "${usb_device}" ]; then
+      USB_DEVICE=dev${usb_device}
+    elif [ -n "${USB_DEVICE}" -a "${1}" ]; then
+      USB_DEVICE=dev`expr ${USB_DEVICE#dev} + 1`
+    fi
+    echo "${USB_DEVICE}"
+  fi
+}
+
 [ "USAGE: adb_wait [timeout]
 
 Returns: waits until the device has returned for adb or optional timeout" ]
 adb_wait() {
   local ret
   if [ -n "${1}" ]; then
-    echo -n ". . . waiting `format_duration ${1}`" ${ANDROID_SERIAL} ${USB_ADDRESS} "${CR}"
+    USB_DEVICE=`usb_devnum --next`
+    echo -n ". . . waiting `format_duration ${1}`" ${ANDROID_SERIAL} ${USB_ADDRESS} ${USB_DEVICE} "${CR}"
     timeout --preserve-status --signal=KILL ${1} adb wait-for-device 2>/dev/null
     ret=${?}
     echo -n "                                                                             ${CR}"
@@ -233,6 +251,7 @@
     adb wait-for-device
     ret=${?}
   fi
+  USB_DEVICE=`usb_devnum`
   if [ 0 = ${ret} -a -n "${ACTIVE_SLOT}" ]; then
     local active_slot=`get_active_slot`
     if [ X"${ACTIVE_SLOT}" != X"${active_slot}" ]; then
@@ -242,12 +261,15 @@
   return ${ret}
 }
 
-[ "USAGE: usb_status > stdout
+[ "USAGE: usb_status > stdout 2> stderr
 
-If adb_wait failed, check if device is in adb, recovery or fastboot mode
-and report status string.
+Assumes referenced right after adb_wait or fastboot_wait failued.
+If wait failed, check if device is in adb, recovery or fastboot mode
+and report status strings like  \"(USB stack borken?)\",
+\"(In fastboot mode)\", \"(In recovery mode)\" or \"(in adb mode)\".
+Additional diagnostics may be provided to the stderr output.
 
-Returns: \"(USB stack borken?)\", \"(In fastboot mode)\" or \"(in adb mode)\"" ]
+Returns: USB status string" ]
 usb_status() {
   if inFastboot; then
     echo "(In fastboot mode)"
@@ -256,7 +278,20 @@
   elif inAdb; then
     echo "(In adb mode)"
   else
-    echo "(USB stack borken?)"
+    echo "(USB stack borken for ${USB_ADDRESS})"
+    USB_DEVICE=`usb_devnum`
+    if [ -n "${USB_DEVICE}" ]; then
+      echo "# lsusb -v -s ${USB_DEVICE#dev}"
+      local D=`lsusb -v -s ${USB_DEVICE#dev} 2>&1`
+      if [ -n "${D}" ]; then
+        echo "${D}"
+      else
+        lsusb -v
+      fi
+    else
+      echo "# lsusb -v (expected device missing)"
+      lsusb -v
+    fi >&2
   fi
 }
 
@@ -268,7 +303,8 @@
   # fastboot has no wait-for-device, but it does an automatic
   # wait and requires (even a nonsensical) command to do so.
   if [ -n "${1}" ]; then
-    echo -n ". . . waiting `format_duration ${1}`" ${ANDROID_SERIAL} ${USB_ADDRESS} "${CR}"
+    USB_DEVICE=`usb_devnum --next`
+    echo -n ". . . waiting `format_duration ${1}`" ${ANDROID_SERIAL} ${USB_ADDRESS} ${USB_DEVICE} "${CR}"
     timeout --preserve-status --signal=KILL ${1} fastboot wait-for-device >/dev/null 2>/dev/null
     ret=${?}
     echo -n "                                                                             ${CR}"
@@ -278,6 +314,7 @@
   fi ||
     inFastboot
   ret=${?}
+  USB_DEVICE=`usb_devnum`
   if [ 0 = ${ret} -a -n "${ACTIVE_SLOT}" ]; then
     local active_slot=`get_active_slot`
     if [ X"${ACTIVE_SLOT}" != X"${active_slot}" ]; then
@@ -293,7 +330,8 @@
 recovery_wait() {
   local ret
   if [ -n "${1}" ]; then
-    echo -n ". . . waiting `format_duration ${1}`" ${ANDROID_SERIAL} ${USB_ADDRESS} "${CR}"
+    USB_DEVICE=`usb_devnum --next`
+    echo -n ". . . waiting `format_duration ${1}`" ${ANDROID_SERIAL} ${USB_ADDRESS} ${USB_DEVICE} "${CR}"
     timeout --preserve-status --signal=KILL ${1} adb wait-for-recovery 2>/dev/null
     ret=${?}
     echo -n "                                                                             ${CR}"
@@ -301,6 +339,7 @@
     adb wait-for-recovery
     ret=${?}
   fi
+  USB_DEVICE=`usb_devnum`
   if [ 0 = ${ret} -a -n "${ACTIVE_SLOT}" ]; then
     local active_slot=`get_active_slot`
     if [ X"${ACTIVE_SLOT}" != X"${active_slot}" ]; then
@@ -631,7 +670,8 @@
   USB_ADDRESS=usb${USB_ADDRESS##*/}
 fi
 [ -z "${ANDROID_SERIAL}${USB_ADDRESS}" ] ||
-  echo "${BLUE}[     INFO ]${NORMAL}" ${ANDROID_SERIAL} ${USB_ADDRESS} >&2
+  USB_DEVICE=`usb_devnum`
+  echo "${BLUE}[     INFO ]${NORMAL}" ${ANDROID_SERIAL} ${USB_ADDRESS} ${USB_DEVICE} >&2
 BUILD_DESCRIPTION=`get_property ro.build.description`
 [ -z "${BUILD_DESCRIPTION}" ] ||
   echo "${BLUE}[     INFO ]${NORMAL} ${BUILD_DESCRIPTION}" >&2
@@ -1206,7 +1246,7 @@
 # Prerequisite is a prepped device from above.
 adb_reboot &&
   adb_wait 2m ||
-  die "lost device after reboot to ro state (USB stack broken?)"
+  die "lost device after reboot to ro state `usb_status`"
 adb_sh grep " /vendor .* rw," /proc/mounts >/dev/null </dev/null &&
   die "/vendor is not read-only"
 adb_su remount vendor </dev/null ||
@@ -1226,7 +1266,7 @@
 done
 adb_reboot &&
   adb_wait 2m ||
-  die "lost device after reboot after wipe (USB stack broken?)"
+  die "lost device after reboot after wipe `usb_status`"
 adb_sh grep " /vendor .* rw," /proc/mounts >/dev/null </dev/null &&
   die "/vendor is not read-only"
 adb_su remount vendor </dev/null ||