diff --git a/qemu-sockets.c b/qemu-sockets.c
index c4c0f65..13c0b93 100644
--- a/qemu-sockets.c
+++ b/qemu-sockets.c
@@ -665,24 +665,28 @@
 int unix_listen_opts(QemuOpts *opts)
 {
     fprintf(stderr, "unix sockets are not available on windows\n");
+    errno = ENOTSUP;
     return -1;
 }
 
 int unix_connect_opts(QemuOpts *opts)
 {
     fprintf(stderr, "unix sockets are not available on windows\n");
+    errno = ENOTSUP;
     return -1;
 }
 
 int unix_listen(const char *path, char *ostr, int olen)
 {
     fprintf(stderr, "unix sockets are not available on windows\n");
+    errno = ENOTSUP;
     return -1;
 }
 
 int unix_connect(const char *path)
 {
     fprintf(stderr, "unix sockets are not available on windows\n");
+    errno = ENOTSUP;
     return -1;
 }