diff --git a/db/migrate/20260226121600_sequent_fix_sequence_number_check.rb b/db/migrate/20260226121600_sequent_fix_sequence_number_check.rb
new file mode 100644
index 00000000..b463d0d1
--- /dev/null
+++ b/db/migrate/20260226121600_sequent_fix_sequence_number_check.rb
@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+class SequentFixSequenceNumberCheck < ActiveRecord::Migration[7.2]
+  def up
+    Sequent::Support::Database.with_search_path(Sequent.configuration.event_store_schema_name) do
+      execute_sql_file 'store_events', version: 5
+    end
+  end
+
+  def down
+    Sequent::Support::Database.with_search_path(Sequent.configuration.event_store_schema_name) do
+      execute_sql_file 'store_events', version: 4
+    end
+  end
+
+  private
+
+  def execute_sql_file(filename, version:)
+    say "Applying '#{filename}' version #{version}", true
+    suppress_messages do
+      execute File.read(
+        File.join(
+          File.dirname(__FILE__),
+          format('sequent/%s_v%02d.sql', filename, version),
+        ),
+      )
+    end
+  end
+end
diff --git a/db/migrate/sequent/store_events_v05.sql b/db/migrate/sequent/store_events_v05.sql
new file mode 100644
index 00000000..f7687abc
--- /dev/null
+++ b/db/migrate/sequent/store_events_v05.sql
@@ -0,0 +1,64 @@
+CREATE OR REPLACE PROCEDURE store_events(_command jsonb, _aggregates_with_events jsonb)
+LANGUAGE plpgsql SET search_path FROM CURRENT AS $$
+DECLARE
+  _command_id commands.id%TYPE;
+  _aggregates jsonb;
+  _aggregate jsonb;
+  _events jsonb;
+  _aggregate_id aggregates.aggregate_id%TYPE;
+  _events_partition_key aggregates.events_partition_key%TYPE;
+  _last_sequence_number events.sequence_number%TYPE;
+  _next_sequence_number events.sequence_number%TYPE;
+BEGIN
+  CALL update_types(_command, _aggregates_with_events);
+
+  _command_id = store_command(_command);
+
+  CALL store_aggregates(_aggregates_with_events);
+
+  FOR _aggregate, _events IN SELECT row->0, row->1 FROM jsonb_array_elements(_aggregates_with_events) AS row
+                             ORDER BY row->0->'aggregate_id', row->1->0->'event_json'->'sequence_number'
+  LOOP
+    _aggregate_id = _aggregate->>'aggregate_id';
+    SELECT events_partition_key INTO STRICT _events_partition_key FROM aggregates WHERE aggregate_id = _aggregate_id FOR NO KEY UPDATE;
+
+    SELECT sequence_number
+      INTO _last_sequence_number
+      FROM events
+     WHERE partition_key = _events_partition_key
+       AND aggregate_id = _aggregate_id
+     ORDER BY 1 DESC
+     LIMIT 1;
+
+    SELECT MIN((event->'event_json'->'sequence_number')::integer)
+      INTO _next_sequence_number
+      FROM jsonb_array_elements(_events) AS event;
+
+    -- Check sequence number of first new event to ensure optimistic locking works correctly
+    -- (otherwise two concurrent transactions could insert events with different first/next
+    -- sequence number and no constraint violation would be raised).
+    IF _last_sequence_number IS NULL AND _next_sequence_number <> 1 THEN
+      RAISE EXCEPTION 'sequence_number of first event must be 1, but was % (aggregate %)', _next_sequence_number, _aggregate_id
+            USING ERRCODE = 'integrity_constraint_violation';
+    ELSIF _last_sequence_number IS NOT NULL AND _next_sequence_number > _last_sequence_number + 1 THEN
+      RAISE EXCEPTION 'sequence_number must be consecutive, but last sequence number was % and next is % (aggregate %)',
+                      _last_sequence_number, _next_sequence_number, _aggregate_id
+            USING ERRCODE = 'integrity_constraint_violation';
+    END IF;
+
+    INSERT INTO events (partition_key, aggregate_id, sequence_number, created_at, command_id, event_type_id, event_json)
+    SELECT _events_partition_key,
+           _aggregate_id,
+           (event->'event_json'->'sequence_number')::integer,
+           (event->>'created_at')::timestamptz,
+           _command_id,
+           (SELECT id FROM event_types WHERE type = event->>'event_type'),
+           (event->'event_json') - '{aggregate_id,created_at,event_type,sequence_number}'::text[]
+      FROM jsonb_array_elements(_events) AS event
+     ORDER BY 1, 2, 3;
+  END LOOP;
+
+  _aggregates = (SELECT jsonb_agg(row->0) FROM jsonb_array_elements(_aggregates_with_events) AS row);
+  CALL update_unique_keys(_aggregates);
+END;
+$$;
diff --git a/db/structure.sql b/db/structure.sql
index 4127bb91..d32a55ab 100644
--- a/db/structure.sql
+++ b/db/structure.sql
@@ -569,7 +569,7 @@ BEGIN
      ORDER BY 1 DESC
      LIMIT 1;
 
-    SELECT MIN(event->'event_json'->>'sequence_number')
+    SELECT MIN((event->'event_json'->'sequence_number')::integer)
       INTO _next_sequence_number
       FROM jsonb_array_elements(_events) AS event;
 
@@ -1588,6 +1588,7 @@ ALTER TABLE ONLY sequent_schema.snapshot_records
 SET search_path TO public,view_schema,sequent_schema;
 
 INSERT INTO "schema_migrations" (version) VALUES
+('20260226121600'),
 ('20260129130000'),
 ('20250815103000'),
 ('20250630113000'),
diff --git a/spec/lib/sequent/core/event_store_spec.rb b/spec/lib/sequent/core/event_store_spec.rb
index 72e58989..b1beb7e3 100644
--- a/spec/lib/sequent/core/event_store_spec.rb
+++ b/spec/lib/sequent/core/event_store_spec.rb
@@ -478,6 +478,36 @@ class MyAggregate < Sequent::Core::AggregateRoot
         )
       end.to raise_error(ActiveRecord::StatementInvalid)
     end
+
+    it 'https://github.com/zilverline/sequent/issues/514 is fixed' do
+      stream = Sequent::Core::EventStream.new(
+        aggregate_type: 'MyAggregate',
+        aggregate_id: Sequent.new_uuid,
+      )
+      events = (1..8).map { |i| MyEvent.new(aggregate_id:, sequence_number: i) }
+
+      event_store.commit_events(
+        Sequent::Core::Command.new(aggregate_id:),
+        [
+          [stream, events],
+        ],
+      )
+
+      expect do
+        event_store.commit_events(
+          Sequent::Core::Command.new(aggregate_id:),
+          [
+            [
+              stream,
+              [
+                MyEvent.new(aggregate_id:, sequence_number: 9),
+                MyEvent.new(aggregate_id:, sequence_number: 10),
+              ],
+            ],
+          ],
+        )
+      end.to change(Sequent::Core::EventRecord, :count).by(2)
+    end
   end
 
   describe '#permanently_delete_events' do