diff --git a/awscli/customizations/s3/subcommands.py b/awscli/customizations/s3/subcommands.py
index f77d7196e488..8fbd06f9c51e 100644
--- a/awscli/customizations/s3/subcommands.py
+++ b/awscli/customizations/s3/subcommands.py
@@ -454,13 +454,18 @@
 
 CHECKSUM_MODE = {
         'name': 'checksum-mode', 'choices': ['ENABLED'],
-        'help_text': 'To retrieve the checksum, this mode must be enabled. If the object has a '
-                     'checksum, it will be verified.'
+        'help_text': (
+            'To retrieve the checksum, this mode must be enabled. If the object has a '
+            'checksum, it will be verified. ENABLED is the only valid value.'
+        )
 }
 
 CHECKSUM_ALGORITHM = {
         'name': 'checksum-algorithm', 'choices': ['CRC64NVME', 'CRC32', 'SHA256', 'SHA1', 'CRC32C'],
-        'help_text': 'Indicates the algorithm used to create the checksum for the object.'
+        'help_text': (
+            'Indicates the algorithm used to create the checksum for the object. '
+            'Valid values: CRC64NVME | CRC32 | SHA256 | SHA1 | CRC32C. Defaults to \'CRC64NVME\'.'
+        )
 }
 
 BUCKET_NAME_PREFIX = {