diff --git a/lib/castle/middleware/authenticating.rb b/lib/castle/middleware/authenticating.rb
index 127adb3..39a4fac 100644
--- a/lib/castle/middleware/authenticating.rb
+++ b/lib/castle/middleware/authenticating.rb
@@ -26,9 +26,11 @@ def call(env)
 
         # [status, headers, body]
         app_result = app.call(env)
+        status, headers = app_result
+        return app_result if app_result.nil?
 
         # Find a matching event from the config
-        mapping = @event_mapping.find_by_rack_request(app_result[0].to_s, path, app_result[1], req, true).first
+        mapping = @event_mapping.find_by_rack_request(status.to_s, path, headers, req, true).first
 
         return app_result if mapping.nil?
 
diff --git a/lib/castle/middleware/sensor.rb b/lib/castle/middleware/sensor.rb
index baad5e5..da64337 100644
--- a/lib/castle/middleware/sensor.rb
+++ b/lib/castle/middleware/sensor.rb
@@ -19,7 +19,6 @@ def initialize(app)
 
       def call(env)
         app_result = app.call(env)
-
         status, headers, body = app_result
 
         return app_result unless qualify_for_adding_cjs?(status, headers)
diff --git a/lib/castle/middleware/tracking.rb b/lib/castle/middleware/tracking.rb
index 112973f..0c22285 100644
--- a/lib/castle/middleware/tracking.rb
+++ b/lib/castle/middleware/tracking.rb
@@ -28,9 +28,11 @@ def call(env)
 
         # [status, headers, body]
         app_result = app.call(env)
+        status, headers = app_result
+        return app_result if app_result.nil?
 
         # Find a matching track event from the config
-        mappings = @event_mapping.find_by_rack_request(app_result[0].to_s, path, app_result[1], req, false)
+        mappings = @event_mapping.find_by_rack_request(status.to_s, path, headers, req, false)
 
         mappings.each do |mapping|
           resource ||= configuration.services.provide_user.call(req, true)
diff --git a/spec/castle/middleware/authenticating_spec.rb b/spec/castle/middleware/authenticating_spec.rb
index f243027..1637bbd 100644
--- a/spec/castle/middleware/authenticating_spec.rb
+++ b/spec/castle/middleware/authenticating_spec.rb
@@ -52,6 +52,13 @@ def params
       allow(::Castle::Middleware::PropertiesProvide).to receive(:call).and_return(properties_provide)
     end
 
+    context 'when response is nil' do
+      let(:response) { nil }
+      let(:mapping) { spy }
+
+      it { expect(call).to be(nil) }
+    end
+
     context 'when a mapping exists' do
       let(:mapping) { spy }
 
diff --git a/spec/castle/middleware/sensor_spec.rb b/spec/castle/middleware/sensor_spec.rb
index 8454e22..d5b84e7 100644
--- a/spec/castle/middleware/sensor_spec.rb
+++ b/spec/castle/middleware/sensor_spec.rb
@@ -75,6 +75,12 @@ def xhr?
   describe '#call' do
     subject { described_class.new(app).call(env) }
 
+    context 'when response is nil' do
+      let(:response) { nil }
+
+      it { is_expected.to be(nil) }
+    end
+
     context 'with HTML body' do
       let(:status) { 200 }
       let(:user) { nil }
diff --git a/spec/castle/middleware/tracking_spec.rb b/spec/castle/middleware/tracking_spec.rb
index 1cab5f5..a0dddc4 100644
--- a/spec/castle/middleware/tracking_spec.rb
+++ b/spec/castle/middleware/tracking_spec.rb
@@ -57,6 +57,13 @@ def path
       allow(::Castle::Middleware::PropertiesProvide).to receive(:call).and_return(properties_provide)
     end
 
+    context 'when response is nil' do
+      let(:response) { nil }
+      let(:mapping) { spy }
+
+      it { expect(call).to be(nil) }
+    end
+
     context 'when a mapping exists' do
       let(:mapping) { spy }