diff --git a/internal/tests/mapconv/output.go b/internal/tests/mapconv/output.go
index 4924846..0d9089c 100644
--- a/internal/tests/mapconv/output.go
+++ b/internal/tests/mapconv/output.go
@@ -43,9 +43,9 @@ func (x X) MarshalJSON() ([]byte, error) {
 
 func (x *X) UnmarshalJSON(input []byte) error {
 	type X struct {
-		Map         *map[replacedString]replacedInt
+		Map         map[replacedString]replacedInt
 		Named       *namedMap2
-		NoConv      *map[string]int
+		NoConv      map[string]int
 		NoConvNamed *namedMap
 	}
 	var dec X
@@ -53,8 +53,8 @@ func (x *X) UnmarshalJSON(input []byte) error {
 		return err
 	}
 	if dec.Map != nil {
-		x.Map = make(map[string]int, len(*dec.Map))
-		for k, v := range *dec.Map {
+		x.Map = make(map[string]int, len(dec.Map))
+		for k, v := range dec.Map {
 			x.Map[string(k)] = int(v)
 		}
 	}
@@ -65,7 +65,7 @@ func (x *X) UnmarshalJSON(input []byte) error {
 		}
 	}
 	if dec.NoConv != nil {
-		x.NoConv = *dec.NoConv
+		x.NoConv = dec.NoConv
 	}
 	if dec.NoConvNamed != nil {
 		x.NoConvNamed = *dec.NoConvNamed
@@ -108,9 +108,9 @@ func (x X) MarshalYAML() (interface{}, error) {
 
 func (x *X) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	type X struct {
-		Map         *map[replacedString]replacedInt
+		Map         map[replacedString]replacedInt
 		Named       *namedMap2
-		NoConv      *map[string]int
+		NoConv      map[string]int
 		NoConvNamed *namedMap
 	}
 	var dec X
@@ -118,8 +118,8 @@ func (x *X) UnmarshalYAML(unmarshal func(interface{}) error) error {
 		return err
 	}
 	if dec.Map != nil {
-		x.Map = make(map[string]int, len(*dec.Map))
-		for k, v := range *dec.Map {
+		x.Map = make(map[string]int, len(dec.Map))
+		for k, v := range dec.Map {
 			x.Map[string(k)] = int(v)
 		}
 	}
@@ -130,7 +130,7 @@ func (x *X) UnmarshalYAML(unmarshal func(interface{}) error) error {
 		}
 	}
 	if dec.NoConv != nil {
-		x.NoConv = *dec.NoConv
+		x.NoConv = dec.NoConv
 	}
 	if dec.NoConvNamed != nil {
 		x.NoConvNamed = *dec.NoConvNamed
@@ -173,9 +173,9 @@ func (x X) MarshalTOML() (interface{}, error) {
 
 func (x *X) UnmarshalTOML(unmarshal func(interface{}) error) error {
 	type X struct {
-		Map         *map[replacedString]replacedInt
+		Map         map[replacedString]replacedInt
 		Named       *namedMap2
-		NoConv      *map[string]int
+		NoConv      map[string]int
 		NoConvNamed *namedMap
 	}
 	var dec X
@@ -183,8 +183,8 @@ func (x *X) UnmarshalTOML(unmarshal func(interface{}) error) error {
 		return err
 	}
 	if dec.Map != nil {
-		x.Map = make(map[string]int, len(*dec.Map))
-		for k, v := range *dec.Map {
+		x.Map = make(map[string]int, len(dec.Map))
+		for k, v := range dec.Map {
 			x.Map[string(k)] = int(v)
 		}
 	}
@@ -195,7 +195,7 @@ func (x *X) UnmarshalTOML(unmarshal func(interface{}) error) error {
 		}
 	}
 	if dec.NoConv != nil {
-		x.NoConv = *dec.NoConv
+		x.NoConv = dec.NoConv
 	}
 	if dec.NoConvNamed != nil {
 		x.NoConvNamed = *dec.NoConvNamed
diff --git a/internal/tests/sliceconv/output.go b/internal/tests/sliceconv/output.go
index 8fd4207..0f6e719 100644
--- a/internal/tests/sliceconv/output.go
+++ b/internal/tests/sliceconv/output.go
@@ -45,10 +45,10 @@ func (x X) MarshalJSON() ([]byte, error) {
 
 func (x *X) UnmarshalJSON(input []byte) error {
 	type X struct {
-		Slice       *[]replacedInt
+		Slice       []replacedInt
 		Named       *namedSlice2
-		ByteString  *[]byte
-		NoConv      *[]int
+		ByteString  []byte
+		NoConv      []int
 		NoConvNamed *namedSlice
 	}
 	var dec X
@@ -56,8 +56,8 @@ func (x *X) UnmarshalJSON(input []byte) error {
 		return err
 	}
 	if dec.Slice != nil {
-		x.Slice = make([]int, len(*dec.Slice))
-		for k, v := range *dec.Slice {
+		x.Slice = make([]int, len(dec.Slice))
+		for k, v := range dec.Slice {
 			x.Slice[k] = int(v)
 		}
 	}
@@ -68,10 +68,10 @@ func (x *X) UnmarshalJSON(input []byte) error {
 		}
 	}
 	if dec.ByteString != nil {
-		x.ByteString = string(*dec.ByteString)
+		x.ByteString = string(dec.ByteString)
 	}
 	if dec.NoConv != nil {
-		x.NoConv = *dec.NoConv
+		x.NoConv = dec.NoConv
 	}
 	if dec.NoConvNamed != nil {
 		x.NoConvNamed = *dec.NoConvNamed
@@ -116,10 +116,10 @@ func (x X) MarshalYAML() (interface{}, error) {
 
 func (x *X) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	type X struct {
-		Slice       *[]replacedInt
+		Slice       []replacedInt
 		Named       *namedSlice2
-		ByteString  *[]byte
-		NoConv      *[]int
+		ByteString  []byte
+		NoConv      []int
 		NoConvNamed *namedSlice
 	}
 	var dec X
@@ -127,8 +127,8 @@ func (x *X) UnmarshalYAML(unmarshal func(interface{}) error) error {
 		return err
 	}
 	if dec.Slice != nil {
-		x.Slice = make([]int, len(*dec.Slice))
-		for k, v := range *dec.Slice {
+		x.Slice = make([]int, len(dec.Slice))
+		for k, v := range dec.Slice {
 			x.Slice[k] = int(v)
 		}
 	}
@@ -139,10 +139,10 @@ func (x *X) UnmarshalYAML(unmarshal func(interface{}) error) error {
 		}
 	}
 	if dec.ByteString != nil {
-		x.ByteString = string(*dec.ByteString)
+		x.ByteString = string(dec.ByteString)
 	}
 	if dec.NoConv != nil {
-		x.NoConv = *dec.NoConv
+		x.NoConv = dec.NoConv
 	}
 	if dec.NoConvNamed != nil {
 		x.NoConvNamed = *dec.NoConvNamed
@@ -187,10 +187,10 @@ func (x X) MarshalTOML() (interface{}, error) {
 
 func (x *X) UnmarshalTOML(unmarshal func(interface{}) error) error {
 	type X struct {
-		Slice       *[]replacedInt
+		Slice       []replacedInt
 		Named       *namedSlice2
-		ByteString  *[]byte
-		NoConv      *[]int
+		ByteString  []byte
+		NoConv      []int
 		NoConvNamed *namedSlice
 	}
 	var dec X
@@ -198,8 +198,8 @@ func (x *X) UnmarshalTOML(unmarshal func(interface{}) error) error {
 		return err
 	}
 	if dec.Slice != nil {
-		x.Slice = make([]int, len(*dec.Slice))
-		for k, v := range *dec.Slice {
+		x.Slice = make([]int, len(dec.Slice))
+		for k, v := range dec.Slice {
 			x.Slice[k] = int(v)
 		}
 	}
@@ -210,10 +210,10 @@ func (x *X) UnmarshalTOML(unmarshal func(interface{}) error) error {
 		}
 	}
 	if dec.ByteString != nil {
-		x.ByteString = string(*dec.ByteString)
+		x.ByteString = string(dec.ByteString)
 	}
 	if dec.NoConv != nil {
-		x.NoConv = *dec.NoConv
+		x.NoConv = dec.NoConv
 	}
 	if dec.NoConvNamed != nil {
 		x.NoConvNamed = *dec.NoConvNamed
diff --git a/typeutil.go b/typeutil.go
index 774272e..3a68dc8 100644
--- a/typeutil.go
+++ b/typeutil.go
@@ -98,10 +98,20 @@ func underlyingMap(typ types.Type) *types.Map {
 
 func ensureNilCheckable(typ types.Type) types.Type {
 	orig := typ
+	named := false
 	for {
 		switch typ.(type) {
 		case *types.Named:
 			typ = typ.Underlying()
+			named = true
+		case *types.Slice, *types.Map:
+			if named {
+				// Named slices, maps, etc. are special because they can have a custom
+				// decoder function that prevents the JSON null value. Wrap them with a
+				// pointer to allow null always so required/optional works as expected.
+				return types.NewPointer(orig)
+			}
+			return orig
 		case *types.Pointer, *types.Interface:
 			return orig
 		default: