diff --git a/src/sip/sip_utils.cpp b/src/sip/sip_utils.cpp
index 52aba606624ff5e259ce650b805ca197accce2a3..006b80c55a48dcaa4bc3c3bed0f4145775b2cc69 100644
--- a/src/sip/sip_utils.cpp
+++ b/src/sip/sip_utils.cpp
@@ -49,7 +49,7 @@ PjsipErrorCategory::message( int condition ) const
 {
     std::string err_msg;
     err_msg.reserve(PJ_ERR_MSG_SIZE);
-    err_msg.resize(pj_strerror(condition, &err_msg[0], err_msg.size()).slen);
+    err_msg.resize(pj_strerror(condition, &err_msg[0], err_msg.capacity()).slen);
     return err_msg;
 }