diff --git a/src/plugins/tls/schannel/CMakeLists.txt b/src/plugins/tls/schannel/CMakeLists.txt
index 9a53bf9ee6..a7f7fcd99f 100644
--- a/src/plugins/tls/schannel/CMakeLists.txt
+++ b/src/plugins/tls/schannel/CMakeLists.txt
@@ -29,4 +29,6 @@ qt_internal_add_plugin(QSchannelBackendPlugin
         secur32
         bcrypt
         ncrypt
+    DEFINES
+        QT_NO_CAST_FROM_ASCII
 )