fix log message
diff --git a/src/core/ngx_log.c b/src/core/ngx_log.c
index 175190c..280ead0 100644
--- a/src/core/ngx_log.c
+++ b/src/core/ngx_log.c
@@ -279,7 +279,7 @@
 
                 if (log->log_level != 0) {
                     ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
-                                       "invalid log level \"%s\"",
+                                       "duplicate log level \"%s\"",
                                        value[i].data);
                     return NGX_CONF_ERROR;
                 }