diff --git a/api-builder.cabal b/api-builder.cabal
--- a/api-builder.cabal
+++ b/api-builder.cabal
@@ -1,5 +1,5 @@
 name: api-builder
-version: 0.7.3.0
+version: 0.7.4.0
 synopsis: Library for easily building REST API wrappers in Haskell
 license: BSD3
 license-file: LICENSE
@@ -18,7 +18,7 @@
 source-repository this
   type: git
   location: git://github.com/intolerable/api-builder.git
-  tag: v0.7.3.0
+  tag: v0.7.4.0
 
 library
   exposed-modules:
diff --git a/src/Network/API/Builder/Error.hs b/src/Network/API/Builder/Error.hs
--- a/src/Network/API/Builder/Error.hs
+++ b/src/Network/API/Builder/Error.hs
@@ -1,6 +1,7 @@
 module Network.API.Builder.Error
   ( APIError(..) ) where
 
+import Data.Monoid
 import Network.HTTP.Conduit (HttpException)
 
 -- | Error type for the @API@, where @a@ is the type that should be returned when