diff --git a/core/encoding.c b/core/encoding.c
index 6c69b15..ca317d1 100644
--- a/core/encoding.c
+++ b/core/encoding.c
@@ -1179,7 +1179,7 @@ bool fx_wchar_is_alpha(fx_wchar c)
 
 bool fx_wchar_is_hex_digit(fx_wchar c)
 {
-	return isxdigit(c);
+	return iswxdigit(c);
 }
 
 bool fx_wchar_is_space(fx_wchar c)