diff --git a/src/tools/tor-gencert.c b/src/tools/tor-gencert.c
index b5c96e556a..2d92e1ee8b 100644
--- a/src/tools/tor-gencert.c
+++ b/src/tools/tor-gencert.c
@@ -9,7 +9,9 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
+#ifdef HAVE_UNISTD_H
 #include <unistd.h>
+#endif
 
 #include <openssl/evp.h>
 #include <openssl/pem.h>