diff --git a/Telegram/SourceFiles/boxes/connection_box.cpp b/Telegram/SourceFiles/boxes/connection_box.cpp
index e5d4d9ce5d..1bdb77d824 100644
--- a/Telegram/SourceFiles/boxes/connection_box.cpp
+++ b/Telegram/SourceFiles/boxes/connection_box.cpp
@@ -153,9 +153,13 @@ void AddProxyFromClipboard(
 				const auto type = isSocks
 					? ProxyData::Type::Socks5
 					: ProxyData::Type::Mtproto;
-				const auto fields = url_parse_params(
+				auto fields = url_parse_params(
 					match->captured(1),
 					qthelp::UrlParamNameTransform::ToLower);
+				if (type == ProxyData::Type::Mtproto) {
+					auto &secret = fields[u"secret"_q];
+					secret.replace('+', '-').replace('/', '_');
+				}
 				const auto proxy = ProxyDataFromFields(type, fields);
 				if (!proxy) {
 					const auto status = proxy.status();
diff --git a/Telegram/SourceFiles/core/local_url_handlers.cpp b/Telegram/SourceFiles/core/local_url_handlers.cpp
index 4222b11967..b3ea2eedb6 100644
--- a/Telegram/SourceFiles/core/local_url_handlers.cpp
+++ b/Telegram/SourceFiles/core/local_url_handlers.cpp
@@ -388,6 +388,8 @@ bool ApplyMtprotoProxy(
 	auto params = url_parse_params(
 		match->captured(1),
 		qthelp::UrlParamNameTransform::ToLower);
+	auto &secret = params[u"secret"_q];
+	secret.replace('+', '-').replace('/', '_');
 	ProxiesBoxController::ShowApplyConfirmation(
 		controller,
 		MTP::ProxyData::Type::Mtproto,