diff --git a/config/mh-mingw b/config/mh-mingw
index a795096f038f..e91367a71128 100644
--- a/config/mh-mingw
+++ b/config/mh-mingw
@@ -1,7 +1,9 @@
 # Add -D__USE_MINGW_ACCESS to enable the built compiler to work on Windows
 # Vista (see PR33281 for details).
 BOOT_CFLAGS += -D__USE_MINGW_ACCESS -Wno-pedantic-ms-format
+BOOT_CXXFLAGS += -D__USE_MINGW_ACCESS -Wno-pedantic-ms-format
 CFLAGS += -D__USE_MINGW_ACCESS
+CXXFLAGS += -D__USE_MINGW_ACCESS
 STAGE1_CXXFLAGS += -D__USE_MINGW_ACCESS
 STAGE2_CXXFLAGS += -D__USE_MINGW_ACCESS
 STAGE3_CXXFLAGS += -D__USE_MINGW_ACCESS