diff --git a/ctlrpc.go b/ctlrpc.go
index 94aafd0..0b930bb 100644
--- a/ctlrpc.go
+++ b/ctlrpc.go
@@ -13,12 +13,22 @@ type ControlRPC struct {
 }
 
 // Start a server
-func (c *ControlRPC) Start(in *int, out *int) os.Error {
+func (c *ControlRPC) Start(Id int64, out *int) os.Error {
+	server, exists := servers[Id]
+	if !exists {
+		return os.NewError("no such server")
+	}
+	_ = server
 	return nil
 }
 
 // Stop a server
-func (c *ControlRPC) Stop(in *int, out *int) os.Error {
+func (c *ControlRPC) Stop(Id int64, out *int) os.Error {
+	server, exists := servers[Id]
+	if !exists {
+		return os.NewError("no such server")
+	}
+	_ = server
 	return nil
 }
 
@@ -30,7 +40,11 @@ type ConfigValue struct {
 
 // Set a config value
 func (c *ControlRPC) SetConfig(in *ConfigValue, out *ConfigValue) os.Error {
-	servers[in.Id].cfg.Set(in.Key, in.Value)
+	server, exists := servers[in.Id]
+	if !exists {
+		return os.NewError("no such server")
+	}
+	server.cfg.Set(in.Key, in.Value)
 	out.Id = in.Id
 	out.Key = in.Key
 	out.Value = in.Value
@@ -39,8 +53,12 @@ func (c *ControlRPC) SetConfig(in *ConfigValue, out *ConfigValue) os.Error {
 
 // Get a config value
 func (c *ControlRPC) GetConfig(in *ConfigValue, out *ConfigValue) os.Error {
+	server, exists := servers[in.Id]
+	if !exists {
+		return os.NewError("no such server")
+	}
 	out.Id = in.Id
 	out.Key = in.Key
-	out.Value = servers[in.Id].cfg.StringValue(in.Key)
+	out.Value = server.cfg.StringValue(in.Key)
 	return nil
 }