diff --git a/libports/include/libc-plugin/fd_alloc.h b/libports/include/libc-plugin/fd_alloc.h
index 19d8d6beb2..4d8832ed81 100644
--- a/libports/include/libc-plugin/fd_alloc.h
+++ b/libports/include/libc-plugin/fd_alloc.h
@@ -16,6 +16,7 @@
 #define _LIBC_PLUGIN__FD_ALLOC_H_
 
 #include <base/allocator_avl.h>
+#include <base/lock.h>
 #include <base/printf.h>
 #include <os/path.h>
 
@@ -42,6 +43,7 @@ namespace Libc {
 		char           *fd_path;    /* for 'fchdir()' */
 		Plugin         *plugin;
 		Plugin_context *context;
+		Genode::Lock    lock;
 
 		void path(char const *newpath)
 		{
diff --git a/libports/src/lib/libc/fd_alloc.cc b/libports/src/lib/libc/fd_alloc.cc
index e2b8c4eb24..f82033e44c 100644
--- a/libports/src/lib/libc/fd_alloc.cc
+++ b/libports/src/lib/libc/fd_alloc.cc
@@ -49,7 +49,7 @@ File_descriptor *File_descriptor_allocator::alloc(Plugin *plugin,
 
 	/* allocate fresh fd if the default value for 'libc_fd' was specified */
 	bool alloc_ok = false;
-	if (addr == ANY_FD) 
+	if (addr == ANY_FD)
 		alloc_ok = Allocator_avl_base::alloc(1, reinterpret_cast<void**>(&addr));
 	else
 		alloc_ok = (Allocator_avl_base::alloc_addr(1, addr).is_ok());
@@ -65,6 +65,7 @@ File_descriptor *File_descriptor_allocator::alloc(Plugin *plugin,
 	fdo->fd_path = 0;
 	fdo->plugin  = plugin;
 	fdo->context = context;
+	fdo->lock    = Lock(Lock::UNLOCKED);
 	return fdo;
 }