diff --git a/composite-aeson.cabal b/composite-aeson.cabal
--- a/composite-aeson.cabal
+++ b/composite-aeson.cabal
@@ -3,7 +3,7 @@
 -- see: https://github.com/sol/hpack
 
 name:           composite-aeson
-version:        0.4.0.0
+version:        0.4.1.0
 synopsis:       JSON for Vinyl/Frames records
 description:    Integration between Aeson and Vinyl/Frames records allowing records to be easily converted to JSON using automatic derivation, explicit formats, or a mix of both.
 category:       Records
diff --git a/src/Composite/Aeson/Formats/Default.hs b/src/Composite/Aeson/Formats/Default.hs
--- a/src/Composite/Aeson/Formats/Default.hs
+++ b/src/Composite/Aeson/Formats/Default.hs
@@ -6,6 +6,7 @@
 import Composite.Aeson.Formats.InternalTH (makeTupleDefaults)
 import Composite.Aeson.Formats.Provided -- sorry
 import qualified Data.Aeson as Aeson
+import Data.Fixed (Fixed, HasResolution)
 import Data.Functor.Compose (Compose)
 import Data.Functor.Const (Const)
 import Data.Functor.Identity (Identity)
@@ -73,6 +74,8 @@
   defaultJsonFormat = strictMapJsonFormat id pure defaultJsonFormat
 instance DefaultJsonFormat a => DefaultJsonFormat (HashMap Text a) where
   defaultJsonFormat = strictHashMapJsonFormat id pure defaultJsonFormat
+
+instance HasResolution a => DefaultJsonFormat (Fixed a) where defaultJsonFormat = fixedJsonFormat
 
 $makeTupleDefaults