diff --git a/src/network/ssl/qsslsocket_schannel.cpp b/src/network/ssl/qsslsocket_schannel.cpp
index 91dea3e81cd..eb5c752bed6 100644
--- a/src/network/ssl/qsslsocket_schannel.cpp
+++ b/src/network/ssl/qsslsocket_schannel.cpp
@@ -160,6 +160,7 @@ QT_BEGIN_NAMESPACE
 
 namespace {
 
+bool supportsTls13();
 class SchannelBackend : public QTlsBackend
 {
 private: