diff --git a/src/Yesod/Form/Bootstrap4.hs b/src/Yesod/Form/Bootstrap4.hs
--- a/src/Yesod/Form/Bootstrap4.hs
+++ b/src/Yesod/Form/Bootstrap4.hs
@@ -51,11 +51,6 @@
 withSmallInput fs = fs { fsAttrs = newAttrs }
     where newAttrs = addClass "form-control-sm" (fsAttrs fs)
 
-addClass :: Text -> [(Text, Text)] -> [(Text, Text)]
-addClass klass []                    = [("class", klass)]
-addClass klass (("class", old):rest) = ("class", Data.Text.concat [old, " ", klass]) : rest
-addClass klass (other         :rest) = other : addClass klass rest
-
 data BootstrapGridOptions = ColXs !Int | ColSm !Int | ColMd !Int | ColLg !Int | ColXl !Int
     deriving (Eq, Ord, Show, Read)
 
diff --git a/yesod-form-bootstrap4.cabal b/yesod-form-bootstrap4.cabal
--- a/yesod-form-bootstrap4.cabal
+++ b/yesod-form-bootstrap4.cabal
@@ -1,11 +1,11 @@
--- This file has been generated from package.yaml by hpack version 0.20.0.
+-- This file has been generated from package.yaml by hpack version 0.28.2.
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: d3d64533622b0d3d260186735cd3d0b768de41866516b2d9f91672d9b0cbcc47
+-- hash: 4b546d2b6bb2f659ed486dd26b3b083a9c2713af6e84012067ef2bb008a14606
 
 name:           yesod-form-bootstrap4
-version:        1.0.0
+version:        1.0.1
 synopsis:       renderBootstrap4
 category:       Web
 homepage:       https://github.com/ncaq/yesod-form-bootstrap4#readme