diff --git a/src/util/WCharUtil.hxx b/src/util/WCharUtil.hxx
index 6220f2449..6e387d69a 100644
--- a/src/util/WCharUtil.hxx
+++ b/src/util/WCharUtil.hxx
@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2020 Max Kellermann <max.kellermann@gmail.com>
+ * Copyright 2011-2022 Max Kellermann <max.kellermann@gmail.com>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -116,6 +116,12 @@ IsAlphaNumericASCII(wchar_t ch) noexcept
 	return IsAlphaASCII(ch) || IsDigitASCII(ch);
 }
 
+constexpr bool
+IsLowerAlphaNumericASCII(wchar_t ch) noexcept
+{
+	return IsLowerAlphaASCII(ch) || IsDigitASCII(ch);
+}
+
 /**
  * Convert the specified ASCII character (0x00..0x7f) to upper case.
  * Unlike toupper(), it ignores the system locale.