diff --git a/aos/util/file.h b/aos/util/file.h
index 0c1f11f..385aba7 100644
--- a/aos/util/file.h
+++ b/aos/util/file.h
@@ -3,12 +3,14 @@
 
 #include <string>
 
+#include "absl/strings/string_view.h"
+
 namespace aos {
 namespace util {
 
 // Returns the complete contents of filename. LOG(FATAL)s if any errors are
 // encountered.
-::std::string ReadFileToStringOrDie(const ::std::string &filename);
+::std::string ReadFileToStringOrDie(const absl::string_view filename);
 
 }  // namespace util
 }  // namespace aos