diff --git a/app/controllers/catalog_controller.rb b/app/controllers/catalog_controller.rb
index 4f1f82efe..f89109b2a 100644
--- a/app/controllers/catalog_controller.rb
+++ b/app/controllers/catalog_controller.rb
@@ -789,7 +789,13 @@ def basic_response
 
     def search_service_context
       return {} unless Flipflop.multi_algorithm?
-      return {} unless params[:search_algorithm] == "alternate"
-      { search_builder_class: AlternateSearchBuilder }
+      return {} unless alternate_search_builder_class # use default if none specified
+      { search_builder_class: alternate_search_builder_class }
+    end
+
+    def alternate_search_builder_class
+      "#{params[:search_algorithm]}_search_builder".camelize.constantize
+    rescue NameError
+      nil
     end
 end
diff --git a/spec/controllers/catalog_controller_spec.rb b/spec/controllers/catalog_controller_spec.rb
index aa7bcbf28..b07f1ec2f 100644
--- a/spec/controllers/catalog_controller_spec.rb
+++ b/spec/controllers/catalog_controller_spec.rb
@@ -146,6 +146,14 @@
           expect(repository).to have_received(:search).with(instance_of(AlternateSearchBuilder))
         end
       end
+
+      context "when the search_algorithm parameter is set to 'not_a_real_class'" do
+        it "uses the default search builder" do
+          get :index, params: { q: "coffee", search_algorithm: "not_a_real_class" }
+
+          expect(repository).to have_received(:search).with(instance_of(SearchBuilder))
+        end
+      end
     end
 
     context "when the multi-algorithm feature is off" do