diff --git a/main/sip/sip_client.c b/main/sip/sip_client.c
index cdf698c..87554e0 100644
--- a/main/sip/sip_client.c
+++ b/main/sip/sip_client.c
@@ -204,7 +204,7 @@ static esp_err_t send_register(bool with_auth)
 {
     const device_config_t* config = config_get();
     char buf[SIP_BUFFER_SIZE];
-    char auth_header[512] = "";
+    char auth_header[1024] = "";
 
     generate_branch(s_branch, sizeof(s_branch));
 
@@ -342,7 +342,7 @@ static esp_err_t send_response(int code, const sip_message_t* req)
     }
 
     // To-Tag hinzufügen wenn nicht vorhanden
-    char to_header[256];
+    char to_header[512];
     if (strlen(req->to_tag) > 0) {
         snprintf(to_header, sizeof(to_header), "%s", req->to);
     } else {