diff --git a/trunk/src/protocol/srs_sip_stack.cpp b/trunk/src/protocol/srs_sip_stack.cpp
index e29fc4876..9b8ac1e4b 100644
--- a/trunk/src/protocol/srs_sip_stack.cpp
+++ b/trunk/src/protocol/srs_sip_stack.cpp
@@ -109,7 +109,7 @@ std::string srs_sip_get_param(std::string msg, std::string param)
 
         std::vector<std::string>  v_pram = srs_string_split(value, "=");
         
-        if (v_pram.size() > 0) {
+        if (v_pram.size() > 1) {
             return v_pram.at(1);
         }
     }