diff --git a/include/stdc-predef.h b/include/stdc-predef.h
index af1a2799..5ccd884d 100644
--- a/include/stdc-predef.h
+++ b/include/stdc-predef.h
@@ -7,7 +7,10 @@
 #define __STDC_IEC_559__ 1
 #endif
 
+#undef __STDC_UTF_16__
 #define __STDC_UTF_16__ 1
+
+#undef __STDC_UTF_32__
 #define __STDC_UTF_32__ 1
 
 #endif