diff --git a/lib-src/test-distrib.c b/lib-src/test-distrib.c
index 01897b83a7f..79d899a280c 100644
--- a/lib-src/test-distrib.c
+++ b/lib-src/test-distrib.c
@@ -10,11 +10,14 @@
 
 #include <stdio.h>
 
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+
 #ifndef O_RDONLY
 #define O_RDONLY 0
 #endif
 
-
 /* Break string in two parts to avoid buggy C compilers that ignore characters
    after nulls in strings.  */