diff --git a/headers/posix/uchar.h b/headers/posix/uchar.h
index 72f3ac18cd..8b090cba5e 100644
--- a/headers/posix/uchar.h
+++ b/headers/posix/uchar.h
@@ -1,44 +1,59 @@
 /*
- * Copyright 2018 Haiku, Inc. All Right Reserved
+ * Copyright 2018-2020 Haiku, Inc. All Right Reserved
  * Distributed under the terms of MIT license.
  */
 #ifndef _UCHAR_H
 #define _UCHAR_H
 
+
 #include <wchar.h>
 
+
 #ifdef __cplusplus
 extern "C" {
-#else
-typedef wchar_t char32_t; /* our wchar_t is utf32 */
-typedef wchar_t char16_t;
 #endif
 
-#define __STD_UTF_32__ 1
 
-/* We don't define __STD_UTF_16__, so the format of char16_t is unspecified */
+typedef uint_least32_t char32_t;
+typedef uint_least16_t char16_t;
+
+
+#define __STD_UTF_32__ 1
+#define __STD_UTF_16__ 1
+
+
+// TODO implement mbrtoc16
+
+
 static __inline size_t
-c16rtomb(char *dest, char16_t wc, mbstate_t *mbState)
+c16rtomb(char *dest, char32_t wc, mbstate_t *mbState)
 {
-	return wcrtomb(dest, wc, mbState);
+	wchar_t tmp = (wchar_t)wc;
+	return wcrtomb(dest, tmp, mbState);
 }
+
+
 static __inline size_t
-mbrtoc16(char16_t *dest, const char *src, size_t srcLength, mbstate_t *mbState)
+mbrtoc32(char32_t *dest, const char *src, size_t srcLength, mbstate_t *mbState)
 {
-	return mbrtowc(dest, src, srcLength, mbState);
+	return mbrtowc((wchar_t*)dest, src, srcLength, mbState);
 }
 
+
 static __inline size_t
 c32rtomb(char *dest, char32_t wc, mbstate_t *mbState)
 {
-	return wcrtomb(dest, wc, mbState);
+	return wcrtomb(dest, (wchar_t)wc, mbState);
 }
+
+
 static __inline size_t
 mbrtoc32(char32_t *dest, const char *src, size_t srcLength, mbstate_t *mbState)
 {
-	return mbrtowc(dest, src, srcLength, mbState);
+	return mbrtowc((wchar_t*)dest, src, srcLength, mbState);
 }
 
+
 #ifdef __cplusplus
 }
 #endif