diff --git a/common/rfb/CConnection.cxx b/common/rfb/CConnection.cxx
index f2f19ca..e73b02e 100644
--- a/common/rfb/CConnection.cxx
+++ b/common/rfb/CConnection.cxx
@@ -100,7 +100,7 @@
     char msg[256];
     sprintf(msg,"Server gave unsupported RFB protocol version %d.%d",
             cp.majorVersion, cp.minorVersion);
-    vlog.error(msg);
+    vlog.error("%s", msg);
     state_ = RFBSTATE_INVALID;
     throw Exception(msg);
   } else if (useProtocol3_3 || cp.beforeVersion(3,7)) {
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()
diff --git a/common/rfb/SConnection.cxx b/common/rfb/SConnection.cxx
index 941d30a..ee57336 100644
--- a/common/rfb/SConnection.cxx
+++ b/common/rfb/SConnection.cxx
@@ -239,7 +239,7 @@
 
 void SConnection::throwConnFailedException(const char* msg)
 {
-  vlog.info(msg);
+  vlog.info("%s", msg);
   if (state_ == RFBSTATE_PROTOCOL_VERSION) {
     if (cp.majorVersion == 3 && cp.minorVersion == 3) {
       os->writeU32(0);
diff --git a/common/rfb/SSecurityTLS.cxx b/common/rfb/SSecurityTLS.cxx
index 2ea84e0..9a34f3a 100644
--- a/common/rfb/SSecurityTLS.cxx
+++ b/common/rfb/SSecurityTLS.cxx
@@ -49,7 +49,7 @@
 
 static void debug_log(int level, const char* str)
 {
-  vlog.debug(str);
+  vlog.debug("[%d]: %s", level, str);
 }
 
 void SSecurityTLS::initGlobal()