diff --git a/src/qt/optionsdialog.cpp b/src/qt/optionsdialog.cpp
index dd654a7abe2..4f828c466ce 100644
--- a/src/qt/optionsdialog.cpp
+++ b/src/qt/optionsdialog.cpp
@@ -482,7 +482,10 @@ QValidator(parent)
 QValidator::State ProxyAddressValidator::validate(QString &input, int &pos) const
 {
     Q_UNUSED(pos);
-    // Validate the proxy
+    // "http://x.x.x.x" already prohibited, so safe to fail early here on a ":"
+    if (input.contains(':')) {
+        return QValidator::Invalid;
+    }
     CService serv(LookupNumeric(input.toStdString(), DEFAULT_GUI_PROXY_PORT));
     Proxy addrProxy = Proxy(serv, true);
     if (addrProxy.IsValid())