diff --git a/colorless.cabal b/colorless.cabal
--- a/colorless.cabal
+++ b/colorless.cabal
@@ -3,7 +3,7 @@
 -- see: https://github.com/sol/hpack
 
 name:           colorless
-version:        2.2.0
+version:        2.2.1
 synopsis:       Colorless
 description:    Colorless
 category:       Web
diff --git a/library/Colorless/Client/Expr.hs b/library/Colorless/Client/Expr.hs
--- a/library/Colorless/Client/Expr.hs
+++ b/library/Colorless/Client/Expr.hs
@@ -522,7 +522,7 @@
 instance ToArgs () where
   toArgs _ = []
 
-instance ToAst a => ToArgs (Expr a) where
+instance (ToAst a, HasType a) => ToArgs (Expr a) where
   toArgs x = [toAst x]
 
 instance (HasType t1, ToAst t1, HasType t2, ToAst t2) => ToArgs (t1, t2) where
diff --git a/package.yaml b/package.yaml
--- a/package.yaml
+++ b/package.yaml
@@ -1,5 +1,5 @@
 name: colorless
-version: '2.2.0'
+version: '2.2.1'
 category: Web
 synopsis: Colorless
 description: Colorless