diff --git a/roles/custom/matrix-synapse/tasks/synapse/workers/util/inject_worker.yml b/roles/custom/matrix-synapse/tasks/synapse/workers/util/inject_worker.yml
index 9765be6fc..c52777ebd 100644
--- a/roles/custom/matrix-synapse/tasks/synapse/workers/util/inject_worker.yml
+++ b/roles/custom/matrix-synapse/tasks/synapse/workers/util/inject_worker.yml
@@ -61,7 +61,7 @@
 
 # Inject stream writers into the instance map.
 - ansible.builtin.set_fact:
-    matrix_synapse_instance_map: "{{ matrix_synapse_instance_map | combine({matrix_synapse_worker_details.name: {'host': matrix_synapse_worker_details.name, 'port': matrix_synapse_worker_details.replication_port}}) }}"
+    matrix_synapse_instance_map: "{{ matrix_synapse_instance_map | combine({matrix_synapse_worker_details.name: {'host': matrix_synapse_worker_details.name, 'port': matrix_synapse_worker_details.replication_port | int}}) }}"
   when: matrix_synapse_worker_details.type in matrix_synapse_known_instance_map_eligible_worker_types
 
 # Inject pusher instances.