diff --git a/src/formatUnits.js b/src/formatUnits.js
index dd05d761..d1ca5f7a 100644
--- a/src/formatUnits.js
+++ b/src/formatUnits.js
@@ -144,7 +144,7 @@ register_hook('options_form', def => {
       'FFf': 'DD° MM′ SS.SSS″ X',
       'Ff': 'DD° MM.MMM′ X',
       'f': 'DD.DDD° X',
-      'd': '±DD.DDD'
+      '-d': '±DD.DDD'
     },
     'default': settings.coordFormat
   }