Code style: Replace tab with space.
diff --git a/include/ndn-cpp/forwarding-flags.hpp b/include/ndn-cpp/forwarding-flags.hpp
index 7f06dfd..d722275 100644
--- a/include/ndn-cpp/forwarding-flags.hpp
+++ b/include/ndn-cpp/forwarding-flags.hpp
@@ -6,7 +6,7 @@
  */
 
 #ifndef NDN_FORWARDING_FLAGS_HPP
-#define	NDN_FORWARDING_FLAGS_HPP
+#define NDN_FORWARDING_FLAGS_HPP
 
 #include "c/forwarding-flags.h"