diff --git a/src/util/CharUtil.hxx b/src/util/CharUtil.hxx
index 475dd74b9..7811d9ee8 100644
--- a/src/util/CharUtil.hxx
+++ b/src/util/CharUtil.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
@@ -123,6 +123,12 @@ IsAlphaNumericASCII(char ch) noexcept
 	return IsAlphaASCII(ch) || IsDigitASCII(ch);
 }
 
+constexpr bool
+IsLowerAlphaNumericASCII(char ch) noexcept
+{
+	return IsLowerAlphaASCII(ch) || IsDigitASCII(ch);
+}
+
 /**
  * Convert the specified ASCII character (0x00..0x7f) to upper case.
  * Unlike toupper(), it ignores the system locale.