diff --git a/gpio.cpp b/gpio.cpp
index 855718f..076dee4 100644
--- a/gpio.cpp
+++ b/gpio.cpp
@@ -86,7 +86,7 @@
     {
         auto e = errno;
         log<level::ERR>("Failed opening GPIO device",
-                        entry("DEVICE=%s", device),
+                        entry("DEVICE=%s", device.c_str()),
                         entry("ERRNO=%d", e));
         elog<InternalFailure>();
     }