diff --git a/common/rfb/CSecurityTLS.cxx b/common/rfb/CSecurityTLS.cxx
index 3421de5..6b6b017 100644
--- a/common/rfb/CSecurityTLS.cxx
+++ b/common/rfb/CSecurityTLS.cxx
@@ -72,7 +72,7 @@
 
 static void debug_log(int level, const char* str)
 {
-  vlog_raw.debug(str);
+  vlog_raw.debug("[%d]: %s", level, str);
 }
 
 void CSecurityTLS::initGlobal()