diff --git a/src/config/kbdbind.c b/src/config/kbdbind.c
index e7e5f6de6..da04cf65c 100644
--- a/src/config/kbdbind.c
+++ b/src/config/kbdbind.c
@@ -427,7 +427,7 @@ parse_keystroke(const unsigned char *s, struct term_event_keyboard *kbd)
 		 * and instead make kbd_ev_lookup() or its callers
 		 * search for different variants of the keystroke if
 		 * the original one is not bound to any action.  */
-		kbd->key = toupper(kbd->key);
+		kbd->key = c_toupper(kbd->key);
 	}
 
 	return (kbd->key == KBD_UNDEF) ? -1 : 0;
diff --git a/src/osdep/beos/beos.c b/src/osdep/beos/beos.c
index 79edef6ad..1011013f2 100644
--- a/src/osdep/beos/beos.c
+++ b/src/osdep/beos/beos.c
@@ -41,7 +41,7 @@ get_system_env(void)
 	int env = get_common_env();
 	unsigned char *term = getenv("TERM");
 
-	if (!term || (toupper(term[0]) == 'B' && toupper(term[1]) == 'E'))
+	if (!term || (c_toupper(term[0]) == 'B' && c_toupper(term[1]) == 'E'))
 		env |= ENV_BE;
 
 	return env;