--- a/src/stdlib/SDL_string.c	Sun Mar 06 21:17:09 2011 -0800
+++ b/src/stdlib/SDL_string.c	Sun Mar 06 21:17:44 2011 -0800
@@ -865,8 +865,8 @@
         ++str2;
         --maxlen;
     }
-    a = SDL_tolower(*str1);
-    b = SDL_tolower(*str2);
+    a = SDL_tolower((unsigned char) *str1);
+    b = SDL_tolower((unsigned char) *str2);
     return (int) ((unsigned char) a - (unsigned char) b);
 }
 #endif