diff --git a/b2sdk/_internal/file_lock.py b/b2sdk/_internal/file_lock.py
index 5e95e846..280eddaf 100644
--- a/b2sdk/_internal/file_lock.py
+++ b/b2sdk/_internal/file_lock.py
@@ -73,9 +73,22 @@ def __eq__(self, other):
 
 
 class FileRetentionSetting:
-    """Represent file retention settings, i.e. whether the file is retained, in which mode and until when"""
+    """
+    Represent file retention settings, i.e. whether the file is retained, in which mode and until when
+
+    :param mode: retention mode
+    :type mode: RetentionMode
+    :param retain_until: retain until timestamp (in milliseconds since :abbr:`epoch (1970-01-01 00:00:00)`)
+    :type retain_until: int
+    """
 
     def __init__(self, mode: RetentionMode, retain_until: int | None = None):
+        """
+        :param mode: retention mode
+        :type mode: RetentionMode
+        :param retain_until: retain until timestamp (in milliseconds since :abbr:`epoch (1970-01-01 00:00:00)`)
+        :type retain_until: int
+        """
         if mode in RETENTION_MODES_REQUIRING_PERIODS and retain_until is None:
             raise ValueError(f'must specify retain_until for retention mode {mode}')
         self.mode = mode
diff --git a/changelog.d/532.doc.md b/changelog.d/532.doc.md
new file mode 100644
index 00000000..9dc82669
--- /dev/null
+++ b/changelog.d/532.doc.md
@@ -0,0 +1 @@
+Document params in FileRetentionSetting class.