diff --git a/audio/audio.c b/audio/audio.c
index f24215b..3a30103 100644
--- a/audio/audio.c
+++ b/audio/audio.c
@@ -215,7 +215,7 @@
         pstrcat (r, len + sizeof (qemu_prefix), s);
 
         for (i = 0; i < len; ++i) {
-            u[i] = toupper (u[i]);
+            u[i] = qemu_toupper(u[i]);
         }
     }
     return r;
@@ -470,7 +470,7 @@
 
         /* copy while upper-casing, including trailing zero */
         for (i = 0; i <= preflen; ++i) {
-            optname[i + sizeof (qemu_prefix) - 1] = toupper (prefix[i]);
+            optname[i + sizeof (qemu_prefix) - 1] = qemu_toupper(prefix[i]);
         }
         pstrcat (optname, optlen, "_");
         pstrcat (optname, optlen, opt->name);