diff --git a/registry.go b/registry.go
index 53634d2..4da4922 100644
--- a/registry.go
+++ b/registry.go
@@ -77,19 +77,21 @@ func (rr *rpcRegistry) Invoke(codec protocol.RegistryCodec) (result interface{},
 	// Decode the args.
 
 	var in []reflect.Value
-	paramValues, paramInstances := methodSpec.getParams()
+	paramValues := methodSpec.paramValues
+
 	if nil != paramValues {
-		in = make([]reflect.Value, len(paramValues)+1)
-		if errRead := codec.ReadParams(paramInstances); errRead != nil {
+		params := methodSpec.getInterfaces()
+		if errRead := codec.ReadParams(params); errRead != nil {
 			return nil, errRead
 		}
+		in = make([]reflect.Value, len(paramValues)+1)
 		for indexI := 0; indexI < len(paramValues); indexI++ {
 			in[indexI+1] = paramValues[indexI]
 		}
 	} else {
 		in = make([]reflect.Value, 1)
 	}
-	in[0] = serviceSpec.rcvr
+	in[0] = serviceSpec.rcvrV
 
 	// Call the service method.
 	returnValues := methodSpec.method.Func.Call(in)
diff --git a/service_map.go b/service_map.go
index abe6d8f..5a3e0c1 100644
--- a/service_map.go
+++ b/service_map.go
@@ -19,30 +19,30 @@ var (
 // ----------------------------------------------------------------------------
 
 type service struct {
-	name     string                    // name of service
-	rcvr     reflect.Value             // receiver of methods for the service
-	rcvrType reflect.Type              // type of the receiver
-	methods  map[string]*serviceMethod // registered methods
+	name    string                    // name of service
+	rcvrV   reflect.Value             // receiver of methods for the service
+	rcvrT   reflect.Type              // type of the receiver
+	methods map[string]*serviceMethod // registered methods
 }
 
 type serviceMethod struct {
-	method     reflect.Method // receiver method
-	paramTypes []reflect.Type // type of the request argument
-	returnType reflect.Type   // type of the response argument
+	method      reflect.Method // receiver method
+	paramTypes  []reflect.Type // type of the request argument
+	paramValues []reflect.Value
+	returnType  reflect.Type // type of the response argument
+	returnValue reflect.Value
 }
 
-func (sm *serviceMethod) getParams() (values []reflect.Value, instances []interface{}) {
-	if nil == sm.paramTypes || 0 == len(sm.paramTypes) {
-		return nil, nil
+func (sm *serviceMethod) getInterfaces() (instances []interface{}) {
+	if nil == sm.paramValues || 0 == len(sm.paramValues) {
+		return nil
 	}
 
-	pCount := len(sm.paramTypes)
-	values = make([]reflect.Value, pCount)
+	pCount := len(sm.paramValues)
 	instances = make([]interface{}, pCount)
 
 	for indexI := 0; indexI < pCount; indexI++ {
-		values[indexI] = reflect.New(sm.paramTypes[indexI])
-		instances[indexI] = values[indexI].Interface()
+		instances[indexI] = sm.paramValues[indexI].Interface()
 	}
 
 	return
@@ -62,69 +62,77 @@ type serviceMap struct {
 func (m *serviceMap) register(rcvr interface{}, name string) error {
 	// Setup service.
 	s := &service{
-		name:     name,
-		rcvr:     reflect.ValueOf(rcvr),
-		rcvrType: reflect.TypeOf(rcvr),
-		methods:  make(map[string]*serviceMethod),
+		name:    name,
+		rcvrV:   reflect.ValueOf(rcvr),
+		rcvrT:   reflect.TypeOf(rcvr),
+		methods: make(map[string]*serviceMethod),
 	}
 	if name == "" {
-		s.name = reflect.Indirect(s.rcvr).Type().Name()
+		s.name = reflect.Indirect(s.rcvrV).Type().Name()
 		if !isExported(s.name) {
 			return fmt.Errorf("rpc: type %q is not exported", s.name)
 		}
 	}
 	if s.name == "" {
 		return fmt.Errorf("rpc: no service name for type %q",
-			s.rcvrType.String())
+			s.rcvrT.String())
 	}
 
+	var err error
 	// Setup methods.
 Loop:
-	for i := 0; i < s.rcvrType.NumMethod(); i++ {
-		method := s.rcvrType.Method(i)
-		mtype := method.Type
+	for i := 0; i < s.rcvrT.NumMethod(); i++ {
+		m := s.rcvrT.Method(i)
+		mt := m.Type
 		// Method must be exported.
-		if method.PkgPath != "" {
+		if m.PkgPath != "" {
 			continue
 		}
 
 		var paramTypes []reflect.Type
+		var paramValues []reflect.Value
+		var returnType reflect.Type
+		var returnValue reflect.Value
 
-		mCount := mtype.NumIn()
-		if 0 < mCount {
-			paramTypes = make([]reflect.Type, mCount)
-			for indexI := 1; indexI < mCount; indexI++ {
-				param := mtype.In(indexI)
-				if !isExportedOrBuiltin(param) {
-					continue Loop
+		pCount := mt.NumIn() - 1
+
+		if 0 < pCount {
+			paramTypes = make([]reflect.Type, pCount)
+			paramValues = make([]reflect.Value, pCount)
+
+			for indexI := 0; indexI < pCount; indexI++ {
+				if paramTypes[indexI], paramValues[indexI], err = validateType(mt.In(indexI + 1)); nil != err {
+					return err
 				}
-				paramTypes[indexI] = param.Elem()
 			}
 		}
 
-		var returnType reflect.Type
-		switch mtype.NumOut() {
+		switch mt.NumOut() {
 		case 1:
-			if returnType := mtype.Out(0); returnType != typeOfError {
+			if t := mt.Out(0); t != typeOfError {
 				continue Loop
 			}
 		case 2:
-			if returnType := mtype.Out(0); !isExportedOrBuiltin(returnType) {
+			if t := mt.Out(0); !isExportedOrBuiltin(t) {
 				continue Loop
 			}
 
-			if returnType := mtype.Out(1); returnType != typeOfError {
+			if t := mt.Out(1); t != typeOfError {
 				continue Loop
 			}
-			returnType = mtype.Out(0).Elem()
+			if returnType, returnValue, err = validateType(mt.Out(0)); nil != err {
+				return err
+			}
 		default:
 			continue
 		}
 
-		s.methods[method.Name] = &serviceMethod{
-			method:     method,
-			paramTypes: paramTypes,
-			returnType: returnType,
+		s.methods[m.Name] = &serviceMethod{
+			method:      m,
+			paramTypes:  paramTypes,
+			paramValues: paramValues,
+			returnType:  returnType,
+			returnValue: returnValue,
 		}
 	}
 	if len(s.methods) == 0 {
@@ -142,6 +150,22 @@ Loop:
 	return nil
 }
 
+func validateType(t reflect.Type) (rt reflect.Type, rv reflect.Value, err error) {
+	if t.Kind() == reflect.Struct {
+		err = fmt.Errorf("Type is Struct. Pass by reference, i.e. %s", t)
+		return
+	}
+	if t.Kind() == reflect.Ptr {
+		rt = t.Elem()
+	}
+
+	rv = reflect.New(rt)
+	if rt.Kind() != reflect.Struct {
+		rv = reflect.Indirect(rv)
+	}
+	return
+}
+
 // get returns a registered service given a method name.
 //
 // The method name uses a dotted notation as in "Service.Method".