diff --git a/libc/bionic/mbrtoc32.cpp b/libc/bionic/mbrtoc32.cpp
index f004b78..88a077c 100644
--- a/libc/bionic/mbrtoc32.cpp
+++ b/libc/bionic/mbrtoc32.cpp
@@ -127,7 +127,7 @@
     // Malformed input; redundant encoding.
     return mbstate_reset_and_return_illegal(EILSEQ, state);
   }
-  if ((c32 >= 0xd800 && c32 <= 0xdfff) || c32 == 0xfffe || c32 == 0xffff) {
+  if ((c32 >= 0xd800 && c32 <= 0xdfff) || (c32 > 0x10ffff)) {
     // Malformed input; invalid code points.
     return mbstate_reset_and_return_illegal(EILSEQ, state);
   }