diff --git a/firmware_handler.hpp b/firmware_handler.hpp
index 8d41ba6..1af3d04 100644
--- a/firmware_handler.hpp
+++ b/firmware_handler.hpp
@@ -59,7 +59,7 @@
     std::uint16_t flags;
 
     /** A sesion can be for an image (or tarball) or the hash. */
-    enum State
+    enum class State
     {
         open = 0,
         closed = 1,