diff --git a/dom0/aux-tools/unbind_pci_device.sh b/dom0/aux-tools/unbind_pci_device.sh
index 3995ec06..8df56f2c 100755
--- a/dom0/aux-tools/unbind_pci_device.sh
+++ b/dom0/aux-tools/unbind_pci_device.sh
@@ -29,6 +29,14 @@ BDF=0000:$BDF
 #echo -n "Binding device $BDF to xen-pciback..."
 if [ -e /sys/bus/pci/drivers/pciback/$BDF ]; then
     # Already bound to pciback
+    # Check if device not assigned to any RUNNING VM
+    XS_PATH=/local/domain/0/backend/pci
+    GREP_RE="^$XS_PATH/[0-9]*/[0-9]*/dev-[0-9]* = \"$BDF\""
+    if xenstore-ls -f $XS_PATH | grep -q "$GREP_RE"; then
+        DOMID=`xenstore-ls -f $XS_PATH | grep  "$GREP_RE"|cut -d/ -f7`
+        echo "ERROR: Device already attached to the running VM '`xl domname $DOMID`'" >&2
+        exit 1
+    fi
     exit 0
 fi
 
diff --git a/dom0/qvm-core/qubes.py b/dom0/qvm-core/qubes.py
index cdd99627..3d0f6e96 100755
--- a/dom0/qvm-core/qubes.py
+++ b/dom0/qvm-core/qubes.py
@@ -1372,7 +1372,10 @@ class QubesVm(object):
 
         # Bind pci devices to pciback driver
         for pci in self.pcidevs:
-            subprocess.check_call(['sudo', qubes_pciback_cmd, pci])
+            try:
+                subprocess.check_call(['sudo', qubes_pciback_cmd, pci])
+            except subprocess.CalledProcessError:
+                raise QubesException("Failed to prepare PCI device %s" % pci)
 
         xl_cmdline = ['sudo', '/usr/sbin/xl', 'create', self.conf_file, '-q', '-p']