diff --git a/src/Utils.h b/src/Utils.h
index d306df2..0e5ba14 100644
--- a/src/Utils.h
+++ b/src/Utils.h
@@ -8,6 +8,8 @@
 namespace HoldFast
 {
 
+	// Returns a view into `s`, so the caller must keep that buffer alive for as long
+	// as the returned view is used (do not pass a temporary std::string).
 	[[nodiscard]] inline std::string_view TrimWhitespace(std::string_view s)
 	{
 		const auto first = s.find_first_not_of(" \t\r\n");