diff --git a/acinclude.m4 b/acinclude.m4
index 3ad55c3..089449b 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -1887,6 +1887,8 @@
 #endif
 #ifdef HAVE_SYS_SELECT_H
 #include <sys/select.h>
+#elif defined(HAVE_UNISTD_H)
+#include <unistd.h>
 #endif
 #ifdef HAVE_SYS_SOCKET_H
 #include <sys/socket.h>
@@ -1950,6 +1952,8 @@
 #endif
 #ifdef HAVE_SYS_SELECT_H
 #include <sys/select.h>
+#elif defined(HAVE_UNISTD_H)
+#include <unistd.h>
 #endif
 #ifdef HAVE_SYS_SOCKET_H
 #include <sys/socket.h>
diff --git a/configure.ac b/configure.ac
index 31fc8ff..90a678e 100755
--- a/configure.ac
+++ b/configure.ac
@@ -3887,6 +3887,8 @@
 #endif
 #ifdef HAVE_SYS_SELECT_H
 #include <sys/select.h>
+#elif defined(HAVE_UNISTD_H)
+#include <unistd.h>
 #endif
 #ifdef HAVE_SYS_SOCKET_H
 #include <sys/socket.h>
diff --git a/lib/dict.c b/lib/dict.c
index 208a233..e42165a 100644
--- a/lib/dict.c
+++ b/lib/dict.c
@@ -46,6 +46,8 @@
 
 #ifdef HAVE_SYS_SELECT_H
 #include <sys/select.h>
+#elif defined(HAVE_UNISTD_H)
+#include <unistd.h>
 #endif
 
 #include "urldata.h"
diff --git a/lib/select.c b/lib/select.c
index 1ab0239..857e7f6 100644
--- a/lib/select.c
+++ b/lib/select.c
@@ -24,6 +24,8 @@
 
 #ifdef HAVE_SYS_SELECT_H
 #include <sys/select.h>
+#elif defined(HAVE_UNISTD_H)
+#include <unistd.h>
 #endif
 
 #if !defined(HAVE_SELECT) && !defined(HAVE_POLL_FINE)
diff --git a/lib/transfer.c b/lib/transfer.c
index 7216833..27c984f 100644
--- a/lib/transfer.c
+++ b/lib/transfer.c
@@ -48,6 +48,8 @@
 
 #ifdef HAVE_SYS_SELECT_H
 #include <sys/select.h>
+#elif defined(HAVE_UNISTD_H)
+#include <unistd.h>
 #endif
 
 #ifndef HAVE_SOCKET
diff --git a/src/tool_operate.c b/src/tool_operate.c
index 3c7dd68..e1c9c62 100644
--- a/src/tool_operate.c
+++ b/src/tool_operate.c
@@ -31,6 +31,8 @@
 
 #ifdef HAVE_SYS_SELECT_H
 #  include <sys/select.h>
+#elif defined(HAVE_UNISTD_H)
+#  include <unistd.h>
 #endif
 
 #ifdef __VMS
diff --git a/src/tool_sleep.c b/src/tool_sleep.c
index 67a5443..e842ba9 100644
--- a/src/tool_sleep.c
+++ b/src/tool_sleep.c
@@ -23,6 +23,8 @@
 
 #ifdef HAVE_SYS_SELECT_H
 #  include <sys/select.h>
+#elif defined(HAVE_UNISTD_H)
+#  include <unistd.h>
 #endif
 
 #ifdef HAVE_POLL_H
diff --git a/tests/libtest/test.h b/tests/libtest/test.h
index 4f2af41..4806375 100644
--- a/tests/libtest/test.h
+++ b/tests/libtest/test.h
@@ -36,6 +36,8 @@
 #ifdef HAVE_SYS_SELECT_H
 /* since so many tests use select(), we can just as well include it here */
 #include <sys/select.h>
+#elif defined(HAVE_UNISTD_H)
+#include <unistd.h>
 #endif
 
 #ifdef TPF