diff --git a/src/xenia/kernel/xboxkrnl/xboxkrnl_rtl.cc b/src/xenia/kernel/xboxkrnl/xboxkrnl_rtl.cc
index c1df05979..67bfa3322 100644
--- a/src/xenia/kernel/xboxkrnl/xboxkrnl_rtl.cc
+++ b/src/xenia/kernel/xboxkrnl/xboxkrnl_rtl.cc
@@ -229,8 +229,8 @@ void RtlInitAnsiString_entry(pointer_t<X_ANSI_STRING> destination,
 DECLARE_XBOXKRNL_EXPORT1(RtlInitAnsiString, kNone, kImplemented);
 // https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/wdm/nf-wdm-rtlupcaseunicodechar
 dword_result_t RtlUpcaseUnicodeChar_entry(dword_t SourceCharacter) {
-  return std::use_facet<std::ctype<char16_t>>(std::locale())
-      .toupper(SourceCharacter);
+  return static_cast<uint32_t>(std::towupper(
+      static_cast<wint_t>(static_cast<uint32_t>(SourceCharacter))));
 }
 DECLARE_XBOXKRNL_EXPORT1(RtlUpcaseUnicodeChar, kNone, kImplemented);