diff --git a/src_main/io_devices/pidir.cpp b/src_main/io_devices/pidir.cpp
index 4e306d28..6af7ebd3 100755
--- a/src_main/io_devices/pidir.cpp
+++ b/src_main/io_devices/pidir.cpp
@@ -40,7 +40,9 @@ const PIChar PIDir::separator = '/';
 #    include <dirent.h>
 #  else
 #    ifdef FREERTOS
+extern "C" {
 #      include <sys/dirent.h>
+}
 #    else
 #      include <sys/dir.h>
 #    endif