diff --git a/trunk/src/protocol/srs_sip_stack.hpp b/trunk/src/protocol/srs_sip_stack.hpp
index 8c7e1c9f9..6e6c47d7c 100644
--- a/trunk/src/protocol/srs_sip_stack.hpp
+++ b/trunk/src/protocol/srs_sip_stack.hpp
@@ -55,6 +55,8 @@ enum SrsSipCmdType{
     SrsSipCmdRespone=1
 };
 
+std::string srs_sip_get_utc_date();
+
 class SrsSipRequest
 {
 public: