diff --git a/presence/tach.cpp b/presence/tach.cpp
index 10eb4f2..a784f94 100644
--- a/presence/tach.cpp
+++ b/presence/tach.cpp
@@ -73,7 +73,7 @@
             std::get<int64_t>(s) = 0;
             log<level::INFO>(
                     "Unable to read fan tach sensor.",
-                    entry("SENSOR=%s", tachPath));
+                    entry("SENSOR=%s", tachPath.c_str()));
 
         }
     }