diff --git a/include/bits/prettyprint.hpp b/include/bits/prettyprint.hpp
index 1a27b45..4a78cad 100644
--- a/include/bits/prettyprint.hpp
+++ b/include/bits/prettyprint.hpp
@@ -7,8 +7,8 @@
 //
 // The global operator<< overload hs been removed
 
-#ifndef SOI_PRETTY_PRINT
-#define SOI_PRETTY_PRINT
+#ifndef SOI_HEADER_PRETTY_PRINT
+#define SOI_HEADER_PRETTY_PRINT
 
 #include <cstddef>
 #include <iterator>
@@ -493,4 +493,4 @@ pretty_print(std::basic_ostream<TChar, TCharTraits> &stream,
 
 } // namespace soi
 
-#endif // SOI_PRETTY_PRETTY_PRINT
+#endif // SOI_HEADER_PRETTY_PRETTY_PRINT
diff --git a/include/bits/soi-dbg.hpp b/include/bits/soi-dbg.hpp
index 1cab972..15227d4 100644
--- a/include/bits/soi-dbg.hpp
+++ b/include/bits/soi-dbg.hpp
@@ -7,8 +7,8 @@
 // initialize with dbg_init() to enable colorized output
 //
 
-#ifndef SOI_DBG
-#define SOI_DBG
+#ifndef SOI_HEADER_DBG
+#define SOI_HEADER_DBG
 
 #include <cstddef>
 #include <cstring>
@@ -239,4 +239,4 @@ template <typename T> T &&identity(T &&t) { return std::forward<T>(t); }
 #define dbg(...) SOI_DBG_IMPL(SOI_IS_NONEMPTY(__VA_ARGS__), __VA_ARGS__)
 #endif
 
-#endif // SOI_DBG
+#endif // SOI_HEADER_DBG
diff --git a/include/bits/soi-deprecate.hpp b/include/bits/soi-deprecate.hpp
index b934c2f..cfe8a9e 100644
--- a/include/bits/soi-deprecate.hpp
+++ b/include/bits/soi-deprecate.hpp
@@ -2,6 +2,9 @@
 // Distributed under the Boost Software License, Version 1.0.
 //    (See accompanying file LICENSE_1_0.txt or copy at
 //          http://www.boost.org/LICENSE_1_0.txt)
+#ifndef SOI_HEADER_DEPRECATE
+#define SOI_HEADER_DEPRECATE
+
 #pragma GCC diagnostic error "-Wdeprecated-declarations"
 
 struct endl_is_evil_t {
@@ -86,3 +89,5 @@ free(void *ptr, std::size_t new_size);
 //operator new(std::size_t sz);
 //[[deprecated("delete is evil.  Use a vector.")]] void
 //operator delete(void *ptr) noexcept;
+
+#endif // SOI_HEADER_DEPRECATE
diff --git a/include/bits/soi-io.hpp b/include/bits/soi-io.hpp
index ad307c9..d66f091 100644
--- a/include/bits/soi-io.hpp
+++ b/include/bits/soi-io.hpp
@@ -2,6 +2,9 @@
 // Distributed under the Boost Software License, Version 1.0.
 //    (See accompanying file LICENSE_1_0.txt or copy at
 //          http://www.boost.org/LICENSE_1_0.txt)
+#ifndef SOI_HEADER_IO
+#define SOI_HEADER_IO
+
 #include <iostream>
 #include <cassert>
 #include <vector>
@@ -93,3 +96,5 @@ void print(Arg&& arg, Args&&... args) {
 void print() {
   std::cout << '\n';
 }
+
+#endif // SOI_HEADER_IO
diff --git a/include/bits/soi-redirect.hpp b/include/bits/soi-redirect.hpp
index 7267883..95b5059 100644
--- a/include/bits/soi-redirect.hpp
+++ b/include/bits/soi-redirect.hpp
@@ -2,6 +2,9 @@
 // Distributed under the Boost Software License, Version 1.0.
 //    (See accompanying file LICENSE_1_0.txt or copy at
 //          http://www.boost.org/LICENSE_1_0.txt)
+#ifndef SOI_HEADER_REDIRECT
+#define SOI_HEADER_REDIRECT
+
 #include <ostream>
 #include <streambuf>
 
@@ -95,3 +98,4 @@ void redirect_input(const char *filename) {
 void redirect_input(std::string const &filename) {
   redirect_input(filename.c_str());
 }
+#endif // SOI_HEADER_REDIRECT
diff --git a/include/soi b/include/soi
index 7f09e77..d959663 100644
--- a/include/soi
+++ b/include/soi
@@ -1,14 +1,11 @@
 // -*- c++ -*-
-/*
-   Students: please don't try to understand the details of headers just
-   yet.  All will be explained.  This header is primarily used so that you don't
-   have to understand every concept all at once.
-*/
 //          Copyright Johannes Kapfhammer 2019-2022.
 // Distributed under the Boost Software License, Version 1.0.
 //    (See accompanying file LICENSE_1_0.txt or copy at
 //          http://www.boost.org/LICENSE_1_0.txt)
 
+#ifndef SOI_HEADER_INCLUDED
+#define SOI_HEADER_INCLUDED
 
 #include "bits/include-all.hpp"
 
@@ -93,3 +90,5 @@ using soi::interactive_task;
 
 #define int int64_t
 using namespace std;
+
+#endif // SOI_HEADER_INCLUDED