diff --git a/mailbox-core/src/main/java/org/briarproject/mailbox/core/settings/Settings.kt b/mailbox-core/src/main/java/org/briarproject/mailbox/core/settings/Settings.kt
index 01ace732dbcdb82e04f1abaf9034819350121509..bd64f02c504c0bc3d105758159cf88d3b3bbf99a 100644
--- a/mailbox-core/src/main/java/org/briarproject/mailbox/core/settings/Settings.kt
+++ b/mailbox-core/src/main/java/org/briarproject/mailbox/core/settings/Settings.kt
@@ -4,11 +4,17 @@ import java.util.Hashtable
 
 class Settings : Hashtable<String, String>() {
 
+    /**
+     * Note that null values will get stored as empty string.
+     */
     override fun put(key: String, value: String?): String? {
         return if (value == null) super.put(key, "")
         else super.put(key, value)
     }
 
+    /**
+     * Note that empty strings get returned as null.
+     */
     override fun get(key: String): String? {
         val value = super.get(key)
         return if (value.isNullOrEmpty()) null