diff --git a/src/fleet/azext_fleet/custom.py b/src/fleet/azext_fleet/custom.py
index 08cab2eea18..8d2357c6e68 100644
--- a/src/fleet/azext_fleet/custom.py
+++ b/src/fleet/azext_fleet/custom.py
@@ -288,11 +288,11 @@ def create_update_run(cmd,
 
     managed_cluster_upgrade_spec = managed_cluster_upgrade_spec_model(
         type=upgrade_type, kubernetes_version=kubernetes_version)
-    node_image_selection = node_image_selection_model(type=node_image_selection)
+    node_image_selection_type = node_image_selection_model(type=node_image_selection)
 
     managed_cluster_update = managed_cluster_update_model(
         upgrade=managed_cluster_upgrade_spec,
-        nodeImageSelection=node_image_selection)
+        node_image_selection=node_image_selection_type)
 
     update_run = update_run_model(
         update_strategy_id=update_strategy_id,