diff --git a/handler/handler.go b/handler/handler.go
index 975dd12..921d18a 100644
--- a/handler/handler.go
+++ b/handler/handler.go
@@ -102,7 +102,6 @@ var (
 type FuncInfo struct {
 	Type         reflect.Type // the complete function type
 	Argument     reflect.Type // the non-context argument type, or nil
-	IsVariadic   bool         // true if the function is variadic on its argument
 	Result       reflect.Type // the non-error result type, or nil
 	ReportsError bool         // true if the function reports an error
 	strictFields bool         // enforce strict field checking
@@ -214,12 +213,7 @@ func (fi *FuncInfo) Wrap() Func {
 		}
 	}
 
-	f := reflect.ValueOf(fi.fn)
-	call := f.Call
-	if fi.IsVariadic {
-		call = f.CallSlice
-	}
-
+	call := reflect.ValueOf(fi.fn).Call
 	return Func(func(ctx context.Context, req *jrpc2.Request) (interface{}, error) {
 		args, ierr := newInput(reflect.ValueOf(ctx), req)
 		if ierr != nil {
@@ -239,9 +233,6 @@ func (fi *FuncInfo) Wrap() Func {
 //    func(context.Context, X) error
 //    func(context.Context, X) Y
 //    func(context.Context, X) (Y, error)
-//    func(context.Context, ...X) error
-//    func(context.Context, ...X) Y
-//    func(context.Context, ...X) (Y, error)
 //    func(context.Context, *jrpc2.Request) error
 //    func(context.Context, *jrpc2.Request) Y
 //    func(context.Context, *jrpc2.Request) (Y, error)
@@ -277,9 +268,10 @@ func Check(fn interface{}) (*FuncInfo, error) {
 		return nil, errors.New("wrong number of parameters")
 	} else if info.Type.In(0) != ctxType {
 		return nil, errors.New("first parameter is not context.Context")
+	} else if info.Type.IsVariadic() {
+		return nil, errors.New("variadic functions are not supported")
 	} else if np == 2 {
 		info.Argument = info.Type.In(1)
-		info.IsVariadic = info.Type.IsVariadic()
 	}
 
 	// Check return values.
diff --git a/handler/handler_test.go b/handler/handler_test.go
index 0e0eb0d..5963323 100644
--- a/handler/handler_test.go
+++ b/handler/handler_test.go
@@ -15,7 +15,7 @@ import (
 
 func y1(context.Context) (int, error) { return 0, nil }
 
-func y2(_ context.Context, vs ...int) (int, error) { return len(vs), nil }
+func y2(_ context.Context, vs []int) (int, error) { return len(vs), nil }
 
 func y3(context.Context) error { return errors.New("blah") }
 
@@ -41,9 +41,6 @@ func TestCheck(t *testing.T) {
 		{v: func(context.Context, []int) error { return nil }},
 		{v: func(context.Context, []bool) (float64, error) { return 0, nil }},
 		{v: func(context.Context, *argStruct) int { return 0 }},
-		{v: func(context.Context, ...int) error { return nil }},
-		{v: func(context.Context, ...int) bool { return true }},
-		{v: func(context.Context, ...string) (bool, error) { return false, nil }},
 		{v: func(context.Context, *jrpc2.Request) error { return nil }},
 		{v: func(context.Context, *jrpc2.Request) float64 { return 0 }},
 		{v: func(context.Context, *jrpc2.Request) (byte, error) { return '0', nil }},
diff --git a/jhttp/example_test.go b/jhttp/example_test.go
index a3b87d1..9595440 100644
--- a/jhttp/example_test.go
+++ b/jhttp/example_test.go
@@ -16,7 +16,7 @@ import (
 func Example() {
 	// Set up a bridge to demonstrate the API.
 	b := jhttp.NewBridge(handler.Map{
-		"Test": handler.New(func(ctx context.Context, ss ...string) (string, error) {
+		"Test": handler.New(func(ctx context.Context, ss []string) (string, error) {
 			return strings.Join(ss, " "), nil
 		}),
 	}, nil)
diff --git a/jrpc2_test.go b/jrpc2_test.go
index c7eb95b..3a86dd5 100644
--- a/jrpc2_test.go
+++ b/jrpc2_test.go
@@ -65,8 +65,8 @@ func (dummy) Mul(_ context.Context, req struct{ X, Y int }) (int, error) {
 	return req.X * req.Y, nil
 }
 
-// Max has a variadic signature.
-func (dummy) Max(_ context.Context, vs ...int) (int, error) {
+// Max takes a slice of arguments.
+func (dummy) Max(_ context.Context, vs []int) (int, error) {
 	if len(vs) == 0 {
 		return 0, jrpc2.Errorf(code.InvalidParams, "cannot compute max of no elements")
 	}