diff --git a/CHANGELOG.md b/CHANGELOG.md
index c55b1f8e1..013465a6c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -71,6 +71,8 @@ BUG FIXES:
   - providers/virtualbox: Make more internal interactions with VBoxManage
     retryable to avoid spurious VirtualBox errors. [GH-2831]
   - providers/virtualbox: Config validation catches invalid keys. [GH-2843]
+  - providers/virtualbox: Fix network adapter configuration issue if using
+    provider-specific config. [GH-2854]
   - provisioners/chef: When chowning folders, don't follow symlinks.
   - provisioners/docker: Only add SSH user to docker group if the user
     isn't already in it. [GH-2838]
diff --git a/plugins/providers/virtualbox/config.rb b/plugins/providers/virtualbox/config.rb
index c14311d30..19140bac3 100644
--- a/plugins/providers/virtualbox/config.rb
+++ b/plugins/providers/virtualbox/config.rb
@@ -72,8 +72,8 @@ module VagrantPlugins
       #
       # @param [Integer] slot The slot for this network adapter.
       # @param [Symbol] type The type of adapter.
-      def network_adapter(slot, type, *args)
-        @network_adapters[slot] = [type, args]
+      def network_adapter(slot, type, **opts)
+        @network_adapters[slot] = [type, opts]
       end
 
       # Shortcut for setting memory size for the virtual machine.
diff --git a/test/unit/plugins/providers/virtualbox/config_test.rb b/test/unit/plugins/providers/virtualbox/config_test.rb
new file mode 100644
index 000000000..aee442455
--- /dev/null
+++ b/test/unit/plugins/providers/virtualbox/config_test.rb
@@ -0,0 +1,23 @@
+require_relative "../../../base"
+
+require Vagrant.source_root.join("plugins/providers/virtualbox/config")
+
+describe VagrantPlugins::ProviderVirtualBox::Config do
+  context "defaults" do
+    before { subject.finalize! }
+
+    it "should have one NAT adapter" do
+      expect(subject.network_adapters).to eql({
+        1 => [:nat, {}],
+      })
+    end
+  end
+
+  describe "#network_adapter" do
+    it "configures additional adapters" do
+      subject.network_adapter(2, :bridged, auto_config: true)
+      expect(subject.network_adapters[2]).to eql(
+        [:bridged, auto_config: true])
+    end
+  end
+end
diff --git a/test/unit/plugins/providers/virtualbox/synced_folder_test.rb b/test/unit/plugins/providers/virtualbox/synced_folder_test.rb
index 20a3fcfd8..592de0955 100644
--- a/test/unit/plugins/providers/virtualbox/synced_folder_test.rb
+++ b/test/unit/plugins/providers/virtualbox/synced_folder_test.rb
@@ -3,7 +3,6 @@ require Vagrant.source_root.join("test/unit/base")
 
 require Vagrant.source_root.join("plugins/providers/virtualbox/synced_folder")
 
-# TODO(mitchellh): tag with v2
 describe VagrantPlugins::ProviderVirtualBox::SyncedFolder do
   let(:machine) do
     double("machine").tap do |m|