diff --git a/win/winvnc/ManagedListener.cxx b/win/winvnc/ManagedListener.cxx
index f2933bb..e7728bc 100644
--- a/win/winvnc/ManagedListener.cxx
+++ b/win/winvnc/ManagedListener.cxx
@@ -79,7 +79,7 @@
     if (port)
       sock = new network::TcpListener(NULL, port, localOnly);
   } catch (rdr::Exception& e) {
-    vlog.error(e.str());
+    vlog.error("%s", e.str());
   }
   if (sock) {
     if (!localOnly)
diff --git a/win/winvnc/VNCServerWin32.cxx b/win/winvnc/VNCServerWin32.cxx
index b1b9596..36dbcee 100644
--- a/win/winvnc/VNCServerWin32.cxx
+++ b/win/winvnc/VNCServerWin32.cxx
@@ -189,10 +189,10 @@
 
     vlog.debug("Server exited cleanly");
   } catch (rdr::SystemException &s) {
-    vlog.error(s.str());
+    vlog.error("%s", s.str());
     result = s.err;
   } catch (rdr::Exception &e) {
-    vlog.error(e.str());
+    vlog.error("%s", e.str());
   }
 
   { Lock l(runLock);
diff --git a/win/winvnc/winvnc.cxx b/win/winvnc/winvnc.cxx
index 8fba9dc..b906865 100644
--- a/win/winvnc/winvnc.cxx
+++ b/win/winvnc/winvnc.cxx
@@ -87,7 +87,7 @@
   } else {
     if (isError) {
       try {
-        vlog.error(msg);
+        vlog.error("%s", msg);
         return;
       } catch (...) {
       }