diff --git a/lib/app_profiler/middleware.rb b/lib/app_profiler/middleware.rb
index 63947e1d..0b70fe3c 100644
--- a/lib/app_profiler/middleware.rb
+++ b/lib/app_profiler/middleware.rb
@@ -31,7 +31,7 @@ def profile(env, params)
 
       return yield unless before_profile(env, params_hash)
 
-      profile = AppProfiler.run(params_hash, backend: params.backend) do
+      profile = AppProfiler.run(**params_hash) do
         response = yield
       end
 
diff --git a/lib/app_profiler/parameters.rb b/lib/app_profiler/parameters.rb
index 42c197bc..1bdc6696 100644
--- a/lib/app_profiler/parameters.rb
+++ b/lib/app_profiler/parameters.rb
@@ -15,7 +15,7 @@ def initialize(mode: :wall, interval: nil, ignore_gc: false, autoredirect: false
       @interval = [interval&.to_i || DEFAULT_INTERVALS.fetch(@mode.to_s), MIN_INTERVALS.fetch(@mode.to_s)].max
       @ignore_gc = !!ignore_gc
       @autoredirect = autoredirect
-      @backend = backend
+      @backend = backend || AppProfiler::Backend::StackprofBackend::NAME
       @metadata = { context: AppProfiler.context }.merge(metadata)
       @async = async
     end
@@ -30,6 +30,7 @@ def to_h
         interval: @interval,
         ignore_gc: @ignore_gc,
         metadata: @metadata,
+        backend: @backend,
       }
     end
   end
diff --git a/lib/app_profiler/request_parameters.rb b/lib/app_profiler/request_parameters.rb
index c3509d6e..35468194 100644
--- a/lib/app_profiler/request_parameters.rb
+++ b/lib/app_profiler/request_parameters.rb
@@ -51,6 +51,7 @@ def to_h
         mode: mode.to_sym,
         interval: interval.to_i,
         ignore_gc: !!ignore_gc,
+        backend: backend,
         metadata: {
           id: request_id,
           context: context,
diff --git a/test/app_profiler/request_parameters_test.rb b/test/app_profiler/request_parameters_test.rb
index 32a9ea1f..17048353 100644
--- a/test/app_profiler/request_parameters_test.rb
+++ b/test/app_profiler/request_parameters_test.rb
@@ -58,7 +58,8 @@ class RequestParametersTest < TestCase
         })
 
         assert_equal(
-          { mode: mode.to_sym, interval: interval.to_i, ignore_gc: true, metadata: { id: "123", context: "test" } },
+          { mode: mode.to_sym, interval: interval.to_i, backend: :stackprof, ignore_gc: true,
+            metadata: { id: "123", context: "test" }, },
           params.to_h
         )
         assert_predicate(params, :valid?)