diff --git a/ansible/group_vars/nimbus.mainnet.yml b/ansible/group_vars/nimbus.mainnet.yml
index db0b140..4efb117 100644
--- a/ansible/group_vars/nimbus.mainnet.yml
+++ b/ansible/group_vars/nimbus.mainnet.yml
@@ -57,7 +57,9 @@ beacon_node_build_frequency: '*-*-* {{ 12 + idx }}:00:00'
 # Tuning
 beacon_node_cores_per_node: '{{ (ansible_processor_vcpus / nodes_layout[hostname]|length) | round(0, "ceil") | int }}'
 beacon_node_threads: '{{ (node.branch == "libp2p") | ternary(1, beacon_node_cores_per_node) }}'
-beacon_node_rest_allow_origin: '{{ "*" if node.get("public_api") else "" }}'
+# FIXME: Temporary test to debug REST API timeout issues.
+# https://github.com/status-im/nimbus-eth2/issues/5838
+#beacon_node_rest_allow_origin: '{{ "*" if node.get("public_api") else "" }}'
 beacon_node_history_retention: '{{ "archive" if node.get("public_api") else node.get("history", "prune") }}'
 # Monitoring
 beacon_node_validator_monitor_auto: true