diff --git a/src/backends/meta-fd-source.c b/src/backends/meta-fd-source.c
index d66c7b748..73989bf15 100644
--- a/src/backends/meta-fd-source.c
+++ b/src/backends/meta-fd-source.c
@@ -20,6 +20,8 @@
 
 #include "config.h"
 
+#include <unistd.h>
+
 #include "backends/meta-fd-source.h"
 
 typedef struct _MetaFdtSource