diff --git a/common/rfb/Blacklist.cxx b/common/rfb/Blacklist.cxx
index 4590bef..389bc88 100644
--- a/common/rfb/Blacklist.cxx
+++ b/common/rfb/Blacklist.cxx
@@ -42,6 +42,9 @@ Blacklist::~Blacklist() {
 }
 
 bool Blacklist::isBlackmarked(const char* name) {
+  if (!threshold)
+    return false;
+
   BlacklistMap::iterator i = blm.find(name);
   if (i == blm.end()) {
     // Entry is not already black-marked.
diff --git a/unix/xserver/hw/vnc/Xvnc.man b/unix/xserver/hw/vnc/Xvnc.man
index 54cbb63..c23bccd 100644
--- a/unix/xserver/hw/vnc/Xvnc.man
+++ b/unix/xserver/hw/vnc/Xvnc.man
@@ -478,7 +478,7 @@ See the GnuTLS manual for possible values. Default is \fBNORMAL\fP.
 .TP
 .B \-BlacklistThreshold \fIcount\fP
 The number of unauthenticated connection attempts allowed from any individual
-host before that host is black-listed.  Default is 5.
+host before that host is black-listed.  Default is 5. Set to 0 to disable.
 .
 .TP
 .B \-BlacklistTimeout \fIseconds\fP