diff --git a/.changeset/quiet-cycles-shutdown.md b/.changeset/quiet-cycles-shutdown.md
new file mode 100644
index 0000000..11c3120
--- /dev/null
+++ b/.changeset/quiet-cycles-shutdown.md
@@ -0,0 +1,6 @@
+---
+"posthog-ruby": patch
+"posthog-rails": patch
+---
+
+Clear the feature flag call dedupe cache on shutdown.
diff --git a/lib/posthog/client.rb b/lib/posthog/client.rb
index 5f80feb..014badc 100644
--- a/lib/posthog/client.rb
+++ b/lib/posthog/client.rb
@@ -790,6 +790,9 @@ def shutdown
         @worker&.shutdown
         @worker_thread&.join(1)
       end
+      @distinct_id_has_sent_flag_calls_mutex.synchronize do
+        @distinct_id_has_sent_flag_calls.clear
+      end
     end
 
     private
diff --git a/spec/posthog/client_spec.rb b/spec/posthog/client_spec.rb
index 3a4a609..553f236 100644
--- a/spec/posthog/client_spec.rb
+++ b/spec/posthog/client_spec.rb
@@ -1534,6 +1534,14 @@ def run
     end
 
     describe '#shutdown' do
+      it 'clears feature flag call dedupe cache' do
+        client.instance_variable_get(:@distinct_id_has_sent_flag_calls)['user'] = ['flag_true']
+
+        client.shutdown
+
+        expect(client.instance_variable_get(:@distinct_id_has_sent_flag_calls).length).to eq(0)
+      end
+
       it 'is idempotent and stops accepting new events' do
         worker = instance_spy(PostHog::NoopWorker, is_requesting?: false)
         client.instance_variable_set(:@worker, worker)