diff --git a/tests/libtest/lib503.c b/tests/libtest/lib503.c
index f74ad3f38e1a6825bb1424e493e39d027afd568f..2e4f74232bb3608c062cdd7e3ff8e8d66e85802c 100644
--- a/tests/libtest/lib503.c
+++ b/tests/libtest/lib503.c
@@ -5,6 +5,9 @@
 #endif
 #include <sys/time.h>
 #include <sys/types.h>
+#ifdef HAVE_SYS_SELECT_H
+#include <sys/select.h>
+#endif
 
 /*
  * Source code in here hugely as reported in bug report 651460 by
diff --git a/tests/libtest/lib504.c b/tests/libtest/lib504.c
index 7133fc6df22388140900d0db86ed4552e8040215..269c1a231dccda43a517cb818c7cf46a7ddcc1a7 100644
--- a/tests/libtest/lib504.c
+++ b/tests/libtest/lib504.c
@@ -5,6 +5,9 @@
 #endif
 #include <sys/time.h>
 #include <sys/types.h>
+#ifdef HAVE_SYS_SELECT_H
+#include <sys/select.h>
+#endif
 
 /*
  * Source code in here hugely as reported in bug report 651464 by
diff --git a/tests/libtest/lib507.c b/tests/libtest/lib507.c
index f45169496f5814cada7b47bfe1391495a5eb6771..89591f483aba8ced04393cca497fe7183aad53af 100644
--- a/tests/libtest/lib507.c
+++ b/tests/libtest/lib507.c
@@ -1,5 +1,12 @@
 #include "test.h"
 
+#ifdef HAVE_SYS_SOCKET_H
+#include <sys/socket.h>
+#endif
+#ifdef HAVE_SYS_SELECT_H
+#include <sys/select.h>
+#endif
+
 int test(char *URL)
 {
   CURL* curls;
diff --git a/tests/libtest/lib509.c b/tests/libtest/lib509.c
index d1f32e7c6b872f53d3bf64c1e7d9eddb1a194daa..84c4ee5dec8f7c0544713e792ce33447d60796a3 100644
--- a/tests/libtest/lib509.c
+++ b/tests/libtest/lib509.c
@@ -7,6 +7,9 @@
 #endif
 #include <sys/time.h>
 #include <sys/types.h>
+#ifdef HAVE_SYS_SELECT_H
+#include <sys/select.h>
+#endif
 
 #include <openssl/opensslv.h>
 #include <openssl/x509v3.h>