diff --git a/src/plugins/platforms/windows/qwindowscontext.cpp b/src/plugins/platforms/windows/qwindowscontext.cpp
index 777646f22ef..5ca35cd1e4d 100644
--- a/src/plugins/platforms/windows/qwindowscontext.cpp
+++ b/src/plugins/platforms/windows/qwindowscontext.cpp
@@ -486,6 +486,8 @@ QString QWindowsContext::classNamePrefix()
 #  define xstr(s) str(s)
 #  define str(s) #s
         str << xstr(QT_NAMESPACE);
+#  undef str
+#  undef xstr
 #endif
     }
     return result;