diff --git a/tests/boot-serial-test.c b/tests/boot-serial-test.c
index c935d69824bda59f2f0888e70cba5a8da5d63a2c..fa4183de290685483d339df08c8063e30f12ad63 100644
--- a/tests/boot-serial-test.c
+++ b/tests/boot-serial-test.c
@@ -43,12 +43,13 @@ static testdef_t tests[] = {
 static void check_guest_output(const testdef_t *test, int fd)
 {
     bool output_ok = false;
-    int i, nbr, pos = 0;
+    int i, nbr, pos = 0, ccnt;
     char ch;
 
     /* Poll serial output... Wait at most 60 seconds */
     for (i = 0; i < 6000; ++i) {
-        while ((nbr = read(fd, &ch, 1)) == 1) {
+        ccnt = 0;
+        while ((nbr = read(fd, &ch, 1)) == 1 && ccnt++ < 512) {
             if (ch == test->expect[pos]) {
                 pos += 1;
                 if (test->expect[pos] == '\0') {