diff --git a/newlib/ChangeLog b/newlib/ChangeLog
index f7a962ca9..d501fe600 100644
--- a/newlib/ChangeLog
+++ b/newlib/ChangeLog
@@ -1,3 +1,9 @@
+2009-06-09  Corinna Vinschen  <corinna@vinschen.de>
+
+	* libc/ctype/tolower.c (tolower): Cast conversion result from
+	mbtowc/wctomb to unsigned char to avoid negative return values.
+	* libc/ctype/toupper.c (toupper): Ditto.
+
 2009-06-03  IWAMURO Motonori  <deenheart@gmail.com>
 
 	* libc/string/wcwidth.c: Optimize for speed.
diff --git a/newlib/libc/ctype/tolower.c b/newlib/libc/ctype/tolower.c
index 66ba7233c..8a3843ef2 100644
--- a/newlib/libc/ctype/tolower.c
+++ b/newlib/libc/ctype/tolower.c
@@ -67,7 +67,7 @@ _DEFUN(tolower,(c),int c)
       wchar_t wc;
       if (mbtowc (&wc, s, 1) >= 0
 	  && wctomb (s, (wchar_t) towlower ((wint_t) wc)) == 1)
-	c = s[0];
+	c = (unsigned char) s[0];
     }
   return c;
 #else
diff --git a/newlib/libc/ctype/toupper.c b/newlib/libc/ctype/toupper.c
index 1b298d508..2527a69d3 100644
--- a/newlib/libc/ctype/toupper.c
+++ b/newlib/libc/ctype/toupper.c
@@ -66,7 +66,7 @@ _DEFUN(toupper,(c),int c)
       wchar_t wc;
       if (mbtowc (&wc, s, 1) >= 0
 	  && wctomb (s, (wchar_t) towupper ((wint_t) wc)) == 1)
-	c = s[0];
+	c = (unsigned char) s[0];
     }
   return c;
 #else