diff --git a/tests/qtest/ahci-test.c b/tests/qtest/ahci-test.c
index ca4294f44f..5e1954852e 100644
--- a/tests/qtest/ahci-test.c
+++ b/tests/qtest/ahci-test.c
@@ -1443,6 +1443,7 @@ static int prepare_iso(size_t size, unsigned char **buf, char **name)
     ssize_t ret;
     int fd = mkstemp(cdrom_path);
 
+    g_assert(fd != -1);
     g_assert(buf);
     g_assert(name);
     patt = g_malloc(size);