diff --git a/borgmatic/borg/environment.py b/borgmatic/borg/environment.py
index 235c674d..1b14369a 100644
--- a/borgmatic/borg/environment.py
+++ b/borgmatic/borg/environment.py
@@ -2,6 +2,7 @@ OPTION_TO_ENVIRONMENT_VARIABLE = {
     'borg_base_directory': 'BORG_BASE_DIR',
     'borg_config_directory': 'BORG_CONFIG_DIR',
     'borg_cache_directory': 'BORG_CACHE_DIR',
+    'borg_files_cache_ttl': 'BORG_FILES_CACHE_TTL',
     'borg_security_directory': 'BORG_SECURITY_DIR',
     'borg_keys_directory': 'BORG_KEYS_DIR',
     'encryption_passcommand': 'BORG_PASSCOMMAND',
@@ -27,7 +28,7 @@ def make_environment(storage_config):
         value = storage_config.get(option_name)
 
         if value:
-            environment[environment_variable_name] = value
+            environment[environment_variable_name] = str(value)
 
     for (
         option_name,
diff --git a/borgmatic/config/schema.yaml b/borgmatic/config/schema.yaml
index f7161563..af0051b7 100644
--- a/borgmatic/config/schema.yaml
+++ b/borgmatic/config/schema.yaml
@@ -315,6 +315,12 @@ properties:
                     Path for Borg cache files. Defaults to
                     $borg_base_directory/.cache/borg
                 example: /path/to/base/cache
+            borg_files_cache_ttl:
+                type: integer
+                description: |
+                    Maximum time to live (ttl) for entries in the borg files
+                    cache.
+                example: 20
             borg_security_directory:
                 type: string
                 description: |