diff --git a/borgmatic/borg/environment.py b/borgmatic/borg/environment.py
index 90f79cbd..e975ec04 100644
--- a/borgmatic/borg/environment.py
+++ b/borgmatic/borg/environment.py
@@ -13,7 +13,6 @@ OPTION_TO_ENVIRONMENT_VARIABLE = {
     'borg_key_file': 'BORG_KEY_FILE',
     'ssh_command': 'BORG_RSH',
     'temporary_directory': 'TMPDIR',
-    'msgpack_version_check': 'BORG_MSGPACK_VERSION_CHECK',
 }
 
 DEFAULT_BOOL_OPTION_TO_UNCONDITIONAL_ENVIRONMENT_VARIABLE = {
@@ -26,6 +25,7 @@ DEFAULT_BOOL_OPTION_TO_ENVIRONMENT_VARIABLE = {
     'relocated_repo_access_is_ok': 'BORG_RELOCATED_REPO_ACCESS_IS_OK',
     'unknown_unencrypted_repo_access_is_ok': 'BORG_UNKNOWN_UNENCRYPTED_REPO_ACCESS_IS_OK',
     'use_chunks_archive': 'BORG_USE_CHUNKS_ARCHIVE',
+    'msgpack_version_check': 'BORG_MSGPACK_VERSION_CHECK',
 }
 
 
@@ -91,7 +91,8 @@ def make_environment(config):
     ) in DEFAULT_BOOL_OPTION_TO_ENVIRONMENT_VARIABLE.items():
         if os.environ.get(environment_variable_name) is None:
             value = config.get(option_name)
-            environment[environment_variable_name] = 'YES' if value else 'NO'
+            if value is not None:
+                environment[environment_variable_name] = 'YES' if value else 'NO'
 
     for (
         option_name,
diff --git a/tests/unit/borg/test_environment.py b/tests/unit/borg/test_environment.py
index f458cf6a..ee190770 100644
--- a/tests/unit/borg/test_environment.py
+++ b/tests/unit/borg/test_environment.py
@@ -95,6 +95,7 @@ def test_make_environment_without_configuration_sets_certain_environment_variabl
         'BORG_USE_CHUNKS_ARCHIVE': 'NO',
         'BORG_DEBUG_PASSPHRASE': 'NO',
         'BORG_DISPLAY_PASSPHRASE': 'NO',
+        'BORG_MSGPACK_VERSION_CHECK': 'YES',
     }
 
 
@@ -107,6 +108,8 @@ def test_make_environment_without_configuration_passes_through_default_environme
             'BORG_USE_CHUNKS_ARCHIVE': 'yup',
             'BORG_DEBUG_PASSPHRASE': 'nah',
             'BORG_DISPLAY_PASSPHRASE': 'yup',
+            'BORG_MSGPACK_VERSION_CHECK': 'yup',
+
         },
     )
     flexmock(module.borgmatic.hooks.credential.parse).should_receive(
@@ -122,6 +125,7 @@ def test_make_environment_without_configuration_passes_through_default_environme
         'BORG_USE_CHUNKS_ARCHIVE': 'yup',
         'BORG_DEBUG_PASSPHRASE': 'nah',
         'BORG_DISPLAY_PASSPHRASE': 'yup',
+        'BORG_MSGPACK_VERSION_CHECK': 'yup',
         'BORG_EXIT_CODES': 'modern',
     }