diff --git a/lib/vagrant-libvirt/config.rb b/lib/vagrant-libvirt/config.rb
index 3f777b0..ae7de88 100644
--- a/lib/vagrant-libvirt/config.rb
+++ b/lib/vagrant-libvirt/config.rb
@@ -389,6 +389,9 @@ module VagrantPlugins
         # Inputs
         @inputs = [{:type => "mouse", :bus => "ps2"}] if @inputs == UNSET_VALUE
 
+        # PCI device passthrough
+        @pcis = [] if @pcis == UNSET_VALUE
+
         # Suspend mode
         @suspend_mode = "pause" if @suspend_mode == UNSET_VALUE