diff --git a/src/azure-cli/azure/cli/command_modules/acs/_help.py b/src/azure-cli/azure/cli/command_modules/acs/_help.py
index 7f8e02788b9..ae8a912e64d 100644
--- a/src/azure-cli/azure/cli/command_modules/acs/_help.py
+++ b/src/azure-cli/azure/cli/command_modules/acs/_help.py
@@ -780,7 +780,7 @@
     short-summary: Size in GB of the OS disk for each node in the agent pool. Minimum 30 GB.
   - name: --node-osdisk-type
     type: string
-    short-summary: OS disk type to be used for machines in a given agent pool. Defaults to 'Ephemeral' when possible in conjunction with VM size and OS disk size. May not be changed for this pool after creation.
+    short-summary: OS disk type to be used for machines in a given agent pool. Defaults to 'Ephemeral' when possible in conjunction with VM size and OS disk size. May not be changed for this pool after creation. ('Ephemeral' or 'Managed')
   - name: --max-pods -m
     type: int
     short-summary: The maximum number of pods deployable to a node.