diff --git a/SilKit/source/util/StringHelpers.cpp b/SilKit/source/util/StringHelpers.cpp
index fc409199d..08fe20a41 100644
--- a/SilKit/source/util/StringHelpers.cpp
+++ b/SilKit/source/util/StringHelpers.cpp
@@ -96,14 +96,6 @@ auto CurrentTimestampString() -> std::string
     return fmt::format("{:%FT%H-%M-%S}", tm);
 }
 
-auto LowerCase(std::string input) -> std::string
-{
-    // Note: std::tolower has undefined behavior if the argument is not representable as unsigned char.
-    std::transform(input.begin(), input.end(), input.begin(),
-                   [](unsigned char c) { return static_cast<char>(std::tolower(static_cast<int>(static_cast<unsigned char>(c)))); });
-    return input;
-}
-
 auto PrintableString(const std::string& participantName) -> std::string
 {
     std::string safeName;
diff --git a/SilKit/source/util/StringHelpers.hpp b/SilKit/source/util/StringHelpers.hpp
index d75770a6d..549df682d 100644
--- a/SilKit/source/util/StringHelpers.hpp
+++ b/SilKit/source/util/StringHelpers.hpp
@@ -4,10 +4,13 @@
 
 #pragma once
 
+#include <algorithm>
 #include <string>
 #include <string_view>
 #include <vector>
 
+#include <cctype>
+
 
 namespace SilKit {
 namespace Util {
@@ -32,3 +35,19 @@ auto SplitString(std::string_view input, const std::string_view& separator) -> s
 
 } // namespace Util
 } // namespace SilKit
+
+
+namespace SilKit {
+namespace Util {
+
+inline auto LowerCase(std::string input) -> std::string
+{
+    // Note: std::tolower has undefined behavior if the argument is not representable as unsigned char.
+    std::transform(input.begin(), input.end(), input.begin(), [](unsigned char c) {
+        return static_cast<char>(std::tolower(static_cast<int>(static_cast<unsigned char>(c))));
+    });
+    return input;
+}
+
+} // namespace Util
+} // namespace SilKit