diff --git a/include/poll.h b/include/poll.h
index d9b602c..9e1d99a 100644
--- a/include/poll.h
+++ b/include/poll.h
@@ -16,6 +16,7 @@
 #ifndef _FORTIFY_POLL_H
 #define _FORTIFY_POLL_H
 
+__extension__
 #include_next <poll.h>
 
 #if defined(_FORTIFY_SOURCE) && _FORTIFY_SOURCE > 0 && defined(__OPTIMIZE__) && __OPTIMIZE__ > 0
diff --git a/include/stdio.h b/include/stdio.h
index 996c661..1b76f82 100644
--- a/include/stdio.h
+++ b/include/stdio.h
@@ -16,6 +16,7 @@
 #ifndef _FORTIFY_STDIO_H
 #define _FORTIFY_STDIO_H
 
+__extension__
 #include_next <stdio.h>
 
 #if defined(_FORTIFY_SOURCE) && _FORTIFY_SOURCE > 0 && defined(__OPTIMIZE__) && __OPTIMIZE__ > 0
diff --git a/include/stdlib.h b/include/stdlib.h
index 2b67235..f89341f 100644
--- a/include/stdlib.h
+++ b/include/stdlib.h
@@ -16,9 +16,11 @@
 #ifndef _FORTIFY_STDLIB_H
 #define _FORTIFY_STDLIB_H
 
+__extension__
 #include_next <stdlib.h>
 
 #if defined(_XOPEN_SOURCE) || defined(_GNU_SOURCE) || defined(_BSD_SOURCE)
+__extension__
 #include_next <limits.h>
 #endif
 
diff --git a/include/string.h b/include/string.h
index 98bfea1..a4072d6 100644
--- a/include/string.h
+++ b/include/string.h
@@ -16,6 +16,7 @@
 #ifndef _FORTIFY_STRING_H
 #define _FORTIFY_STRING_H
 
+__extension__
 #include_next <string.h>
 
 #if defined(_FORTIFY_SOURCE) && _FORTIFY_SOURCE > 0 && defined(__OPTIMIZE__) && __OPTIMIZE__ > 0
diff --git a/include/sys/select.h b/include/sys/select.h
index db6135d..7f768f4 100644
--- a/include/sys/select.h
+++ b/include/sys/select.h
@@ -16,6 +16,7 @@
 #ifndef _FORTIFY_SYS_SELECT_H
 #define _FORTIFY_SYS_SELECT_H
 
+__extension__
 #include_next <sys/select.h>
 
 #if defined(_FORTIFY_SOURCE) && _FORTIFY_SOURCE > 0 && defined(__OPTIMIZE__) && __OPTIMIZE__ > 0
diff --git a/include/sys/socket.h b/include/sys/socket.h
index e68e21c..9454951 100644
--- a/include/sys/socket.h
+++ b/include/sys/socket.h
@@ -16,6 +16,7 @@
 #ifndef _FORTIFY_SYS_SOCKET_H
 #define _FORTIFY_SYS_SOCKET_H
 
+__extension__
 #include_next <sys/socket.h>
 
 #if defined(_FORTIFY_SOURCE) && _FORTIFY_SOURCE > 0 && defined(__OPTIMIZE__) && __OPTIMIZE__ > 0
diff --git a/include/unistd.h b/include/unistd.h
index 5274e22..5fa3b44 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -16,6 +16,7 @@
 #ifndef _FORTIFY_UNISTD_H
 #define _FORTIFY_UNISTD_H
 
+__extension__
 #include_next <unistd.h>
 
 #if defined(_FORTIFY_SOURCE) && _FORTIFY_SOURCE > 0 && defined(__OPTIMIZE__) && __OPTIMIZE__ > 0
diff --git a/include/wchar.h b/include/wchar.h
index 6fa86f2..0d4abfa 100644
--- a/include/wchar.h
+++ b/include/wchar.h
@@ -16,7 +16,9 @@
 #ifndef _FORTIFY_WCHAR_H
 #define _FORTIFY_WCHAR_H
 
+__extension__
 #include_next <stdlib.h>
+__extension__
 #include_next <wchar.h>
 
 #if defined(_FORTIFY_SOURCE) && _FORTIFY_SOURCE > 0 && defined(__OPTIMIZE__) && __OPTIMIZE__ > 0