diff --git a/server.go b/server.go
index 3e6399d..7e88116 100644
--- a/server.go
+++ b/server.go
@@ -36,7 +36,7 @@ type server struct {
 }
 
 func (s *server) Start() error {
-	if nil != s.serverHandler {
+	if nil == s.serverHandler {
 		panic("Server: server handler must be specified.")
 	}
 	s.serverHandler.Validate()