1 files changed, 1 insertions, 1 deletions

diff --git a/2016/src/day09.cpp b/2016/src/day09.cpp
index 10bf640..825fb05 100644
--- a/2016/src/day09.cpp
+++ b/2016/src/day09.cpp
@@ -4,7 +4,7 @@
 using namespace std;
 
 string
-read_file(string_view filename)
+read_file(const string& filename)
 {
         fstream input{ filename };
         string  line;