diff --git a/lpc_aspeed.hpp b/lpc_aspeed.hpp
index 53fe39b..f3608d0 100644
--- a/lpc_aspeed.hpp
+++ b/lpc_aspeed.hpp
@@ -30,6 +30,7 @@
 
   private:
     static const std::string lpcControlPath;
+    int mappedFd = -1;
     std::uint32_t regionAddress;
     std::size_t regionSize;
     const internal::Sys* sys;