diff --git a/lib/que.rb b/lib/que.rb
index 8cd3db9..7c1bee8 100644
--- a/lib/que.rb
+++ b/lib/que.rb
@@ -64,13 +64,17 @@ def connection=(connection)
           Adapters::ActiveRecord.new
         else
           case connection.class.to_s
-          when "Que::Adapters::ActiveRecordWithLock" then connection
           when "Sequel::Postgres::Database" then Adapters::Sequel.new(connection)
           when "ConnectionPool"             then Adapters::ConnectionPool.new(connection)
           when "PG::Connection"             then Adapters::PG.new(connection)
           when "Pond"                       then Adapters::Pond.new(connection)
           when "NilClass"                   then connection
-          else raise "Que connection not recognized: #{connection.inspect}"
+          else
+            if connection.is_a?(Adapters::Base)
+              connection
+            else
+              raise "Que connection not recognized: #{connection.inspect}"
+            end
           end
         end
     end
diff --git a/spec/lib/que/que_spec.rb b/spec/lib/que/que_spec.rb
new file mode 100644
index 0000000..652560a
--- /dev/null
+++ b/spec/lib/que/que_spec.rb
@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+require "spec_helper"
+
+RSpec.describe Que do
+  describe ".connection=" do
+    it "accepts a custom Adapters::Base subclass instance and sets it as the adapter" do
+      custom_adapter_class = Class.new(Que::Adapters::Base)
+      stub_const("MyApp::CustomAdapter", custom_adapter_class)
+      custom_adapter = MyApp::CustomAdapter.new
+
+      expect { described_class.connection = custom_adapter }.to_not raise_error
+      expect(described_class.adapter).to eq(custom_adapter)
+    end
+
+    it "raises for an unrecognized non-adapter object" do
+      expect { described_class.connection = Object.new }.
+        to raise_error(/Que connection not recognized/)
+    end
+
+    # Named connection-class branches must take priority over the is_a?(Adapters::Base)
+    # fallback. Without this ordering, a Base subclass whose class name happens to match
+    # a known connection type would be passed through as-is instead of being wrapped by
+    # the appropriate adapter.
+    context "when a connection object is both a known named type and an Adapters::Base subclass" do
+      it "wraps it via the named-type branch rather than passing it through as-is" do
+        # Simulate the collision: a class named "ConnectionPool" that also inherits Base.
+        # ConnectionPool adapter is used because its constructor only stores @pool and
+        # does not interact with the connection object at initialisation time.
+        klass = Class.new(Que::Adapters::Base)
+        stub_const("ConnectionPool", klass)
+        connection = ConnectionPool.new
+
+        described_class.connection = connection
+
+        expect(described_class.adapter).to be_a(Que::Adapters::ConnectionPool)
+        expect(described_class.adapter).to_not equal(connection)
+      end
+    end
+  end
+end