diff --git a/lib/vagrant-libvirt/config.rb b/lib/vagrant-libvirt/config.rb
index df6f640..325b38c 100644
--- a/lib/vagrant-libvirt/config.rb
+++ b/lib/vagrant-libvirt/config.rb
@@ -432,7 +432,6 @@ module VagrantPlugins
         # as will the address unit number (unit=0, unit=1, etc)
 
         options = {
-          :dev => self._get_cdrom_dev(@cdroms),
           :bus => "ide",
           :path => nil,
         }.merge(options)
@@ -448,7 +447,6 @@ module VagrantPlugins
 
       def _handle_disk_storage(options={})
         options = {
-          :device => _get_device(@disks),
           :type => 'qcow2',
           :size => '10G',  # matches the fog default
           :path => nil,
@@ -586,7 +584,15 @@ module VagrantPlugins
 
         # Storage
         @disks = [] if @disks == UNSET_VALUE
+        @disks.map! do |disk|
+          disk[:device] = _get_device(@disks) if disk[:device].nil?
+          disk
+        end
         @cdroms = [] if @cdroms == UNSET_VALUE
+        @cdroms.map! do |cdrom|
+          cdrom[:dev] = _get_cdrom_dev(@cdroms) if cdrom[:dev].nil?
+          cdrom
+        end
 
         # Inputs
         @inputs = [{:type => "mouse", :bus => "ps2"}] if @inputs == UNSET_VALUE
@@ -637,6 +643,9 @@ module VagrantPlugins
           c = disks.dup
           c += other.disks
           result.disks = c
+          c = cdroms.dup
+          c += other.cdroms
+          result.cdroms = c
         end
       end
     end
diff --git a/spec/unit/config_spec.rb b/spec/unit/config_spec.rb
new file mode 100644
index 0000000..b6a677f
--- /dev/null
+++ b/spec/unit/config_spec.rb
@@ -0,0 +1,110 @@
+require "spec_helper"
+require "support/sharedcontext"
+
+require "vagrant-libvirt/config"
+
+describe VagrantPlugins::ProviderLibvirt::Config do
+  include_context "unit"
+
+  def assert_invalid
+    errors = subject.validate(machine)
+    if errors.values.any? { |v| !v.empty? }
+      raise "No errors: #{errors.inspect}"
+    end
+  end
+
+  def assert_valid
+    errors = subject.validate(machine)
+    if !errors.values.all? { |v| v.empty? }
+      raise "Errors: #{errors.inspect}"
+    end
+  end
+
+  describe "#validate" do
+    it "is valid with defaults" do
+      assert_valid
+    end
+
+    it "is valid if relative path used for disk" do
+      subject.storage :file, :path => '../path/to/file.qcow2'
+      assert_valid
+    end
+
+    it "should be invalid if absolute path used for disk" do
+      subject.storage :file, :path => '/absolute/path/to/file.qcow2'
+      assert_invalid
+    end
+
+    context "with mac defined" do
+      let (:vm) { double("vm") }
+      let (:networks) { double("networks") }
+      before do
+        allow(vm).to receive(:networks).and_return(networks)
+        allow(machine.config).to receive(:vm).and_return(vm)
+      end
+
+      it "is valid with valid mac" do
+        allow(networks).to receive(:each).and_return([:public, {:mac => "aa:bb:cc:dd:ee:ff"}])
+        assert_valid
+      end
+
+      it "should be invalid if MAC not formatted correctly" do
+        allow(networks).to receive(:each).and_return([:public, {:mac => "aabbccddeeff"}])
+        assert_invalid
+      end
+    end
+  end
+
+  describe "#merge" do
+    let(:one) { described_class.new }
+    let(:two) { described_class.new }
+
+    subject { one.merge(two) }
+
+    context "storage" do
+      context "with disks" do
+        context "assigned specific devices" do
+          it "should merge disks with specific devices" do
+            one.storage(:file, :device => "vdb")
+            two.storage(:file, :device => "vdc")
+            subject.finalize!
+            expect(subject.disks).to include(include(:device => "vdb"),
+                                             include(:device => "vdc"))
+          end
+        end
+
+        context "without devices given" do
+          it "should merge disks with different devices assigned automatically" do
+            one.storage(:file)
+            two.storage(:file)
+            subject.finalize!
+            expect(subject.disks).to include(include(:device => "vdb"),
+                                             include(:device => "vdc"))
+          end
+        end
+      end
+
+      context "with cdroms only" do
+        context "assigned specific devs" do
+          it "should merge disks with specific devices" do
+            one.storage(:file, :device => :cdrom, :dev => "hda")
+            two.storage(:file, :device => :cdrom, :dev => "hdb")
+            subject.finalize!
+            expect(subject.cdroms).to include(include(:dev => "hda"),
+                                              include(:dev => "hdb"))
+          end
+        end
+
+        context "without devs given" do
+          it "should merge cdroms with different devs assigned automatically" do
+            one.storage(:file, :device => :cdrom)
+            two.storage(:file, :device => :cdrom)
+            subject.finalize!
+            expect(subject.cdroms).to include(include(:dev => "hda"),
+                                              include(:dev => "hdb"))
+          end
+        end
+      end
+    end
+  end
+end