diff --git a/redbot/cogs/mod/settings.py b/redbot/cogs/mod/settings.py
index b482c7b64..22864f6d1 100644
--- a/redbot/cogs/mod/settings.py
+++ b/redbot/cogs/mod/settings.py
@@ -377,9 +377,20 @@ class ModSettings(MixinMeta):
     async def defaultduration(
         self,
         ctx: commands.Context,
-        duration: Optional[commands.TimedeltaConverter] = timedelta(days=0),
+        *,
+        duration: commands.TimedeltaConverter(
+            minimum=timedelta(seconds=1), default_unit="seconds"
+        ),
     ):
-        """Set the default time to be used when a user is tempbanned."""
+        """Set the default time to be used when a user is tempbanned.
+
+        Accepts: seconds, minutes, hours, days, weeks
+        `duration` must be greater than zero.
+
+        Examples:
+            `[p]modset defaultduration 7d12h10m`
+            `[p]modset defaultduration 7 days 12 hours 10 minutes`
+        """
         guild = ctx.guild
         await self.config.guild(guild).default_tempban_duration.set(duration.total_seconds())
         await ctx.send(