diff --git a/src/fs_attr.cpp b/src/fs_attr.cpp
index 6a5ea619..47a9291a 100644
--- a/src/fs_attr.cpp
+++ b/src/fs_attr.cpp
@@ -15,7 +15,9 @@
 */
 
 #ifdef __linux__
-# include "fs_attr_linux.icpp"
+#warning "using fs_attr_linux.icpp"
+#include "fs_attr_linux.icpp"
 #else
-# include "fs_attr_unsupported.icpp"
+#warning "using fs_attr_unsupported.icpp"
+#include "fs_attr_unsupported.icpp"
 #endif
diff --git a/src/fs_copy_file_range.cpp b/src/fs_copy_file_range.cpp
index 41300db5..84372ab7 100644
--- a/src/fs_copy_file_range.cpp
+++ b/src/fs_copy_file_range.cpp
@@ -17,7 +17,9 @@
 */
 
 #ifdef __linux__
-# include "fs_copy_file_range_linux.icpp"
+#warning "using fs_copy_file_range_linux.icpp"
+#include "fs_copy_file_range_linux.icpp"
 #else
-# include "fs_copy_file_range_unsupported.icpp"
+#warning "using fs_copy_file_range_unsupported.icpp"
+#include "fs_copy_file_range_unsupported.icpp"
 #endif
diff --git a/src/fs_fadvise.cpp b/src/fs_fadvise.cpp
index 4c093aa5..630df585 100644
--- a/src/fs_fadvise.cpp
+++ b/src/fs_fadvise.cpp
@@ -17,9 +17,11 @@
 #include <fcntl.h>
 
 #if _XOPEN_SOURCE >= 600 || _POSIX_C_SOURCE >= 200112L
-# include "fs_fadvise_posix.icpp"
+#warning "using fs_fadvise_posix.icpp"
+#include "fs_fadvise_posix.icpp"
 #else
-# include "fs_fadvise_unsupported.icpp"
+#warning "using fs_fadvise_unsupported.icpp"
+#include "fs_fadvise_unsupported.icpp"
 #endif
 
 #ifndef POSIX_FADV_NORMAL
diff --git a/src/fs_ficlone.cpp b/src/fs_ficlone.cpp
index 023345d2..58310e20 100644
--- a/src/fs_ficlone.cpp
+++ b/src/fs_ficlone.cpp
@@ -17,7 +17,9 @@
 */
 
 #ifdef __linux__
-# include "fs_ficlone_linux.icpp"
+#warning "using fs_ficlone_linux.icpp"
+#include "fs_ficlone_linux.icpp"
 #else
-# include "fs_ficlone_unsupported.icpp"
+#warning "using fs_ficlone_unsupported.icpp"
+#include "fs_ficlone_unsupported.icpp"
 #endif
diff --git a/src/fs_futimens.hpp b/src/fs_futimens.hpp
index c86e279b..9f223303 100644
--- a/src/fs_futimens.hpp
+++ b/src/fs_futimens.hpp
@@ -23,11 +23,14 @@
 #include <sys/stat.h>
 
 #ifdef __linux__
-# include "fs_futimens_linux.hpp"
+#warning "using fs_futimens_linux.hpp"
+#include "fs_futimens_linux.hpp"
 #elif __FreeBSD__ >= 11
-# include "fs_futimens_freebsd_11.hpp"
+#warning "using fs_futimens_freebsd_11.hpp"
+#include "fs_futimens_freebsd_11.hpp"
 #else
-# include "fs_futimens_generic.hpp"
+#warning "using fs_futimens_generic.hpp"
+#include "fs_futimens_generic.hpp"
 #endif
 
 namespace fs
diff --git a/src/fs_futimesat.cpp b/src/fs_futimesat.cpp
index c88e0966..67867e15 100644
--- a/src/fs_futimesat.cpp
+++ b/src/fs_futimesat.cpp
@@ -17,7 +17,9 @@
 */
 
 #if __APPLE__
-# include "fs_futimesat_osx.icpp"
+#warning "using fs_futimesat_osx.icpp"
+#include "fs_futimesat_osx.icpp"
 #else
-# include "fs_futimesat_generic.icpp"
+#warning "using fs_futimesat_generic.icpp"
+#include "fs_futimesat_generic.icpp"
 #endif
diff --git a/src/fs_sendfile.cpp b/src/fs_sendfile.cpp
index 1af25458..3bb52dec 100644
--- a/src/fs_sendfile.cpp
+++ b/src/fs_sendfile.cpp
@@ -15,7 +15,9 @@
 */
 
 #ifdef __linux__
-# include "fs_sendfile_linux.icpp"
+#warning "using fs_sendfile_linux.icpp"
+#include "fs_sendfile_linux.icpp"
 #else
-# include "fs_sendfile_unsupported.icpp"
+#warning "using fs_sendfile_unsupported.icpp"
+#include "fs_sendfile_unsupported.icpp"
 #endif
diff --git a/src/fs_utimensat.hpp b/src/fs_utimensat.hpp
index 6b103c84..bd44fdf7 100644
--- a/src/fs_utimensat.hpp
+++ b/src/fs_utimensat.hpp
@@ -19,9 +19,12 @@
 #pragma once
 
 #ifdef __linux__
-# include "fs_utimensat_linux.hpp"
+#warning "using fs_utimensat_linux.hpp"
+#include "fs_utimensat_linux.hpp"
 #elif __FreeBSD__
-# include "fs_utimensat_freebsd.hpp"
+#warning "using fs_utimensat_freebsd.hpp"
+#include "fs_utimensat_freebsd.hpp"
 #else
-# include "fs_utimensat_generic.hpp"
+#warning "using fs_utimensat_generic.hpp"
+#include "fs_utimensat_generic.hpp"
 #endif
diff --git a/src/ugid.hpp b/src/ugid.hpp
index 9edde0c6..620e8b45 100644
--- a/src/ugid.hpp
+++ b/src/ugid.hpp
@@ -28,7 +28,9 @@ namespace ugid
 }
 
 #if defined __linux__ and UGID_USE_RWLOCK == 0
+#warning "using ugid_linux.hpp"
 #include "ugid_linux.hpp"
 #else
+#warning "using ugid_rwlock.hpp"
 #include "ugid_rwlock.hpp"
 #endif