Code style: Replace tab with space.
diff --git a/include/ndn-cpp/security/security-exception.hpp b/include/ndn-cpp/security/security-exception.hpp
index f14948f..daf1d61 100644
--- a/include/ndn-cpp/security/security-exception.hpp
+++ b/include/ndn-cpp/security/security-exception.hpp
@@ -7,7 +7,7 @@
  */
 
 #ifndef NDN_SECURITY_EXCEPTION_HPP
-#define	NDN_SECURITY_EXCEPTION_HPP
+#define NDN_SECURITY_EXCEPTION_HPP
 
 #include <exception>
 #include <string>