fixed printing queue messages
diff --git a/aos/common/print_field_helpers.h b/aos/common/print_field_helpers.h
index 48acdf6..50ac01e 100644
--- a/aos/common/print_field_helpers.h
+++ b/aos/common/print_field_helpers.h
@@ -13,13 +13,13 @@
 
   size_t len = 0;
   if (is_signed && val <= 0) {
-    while (*output > len && (val != 0 || len == 0)) {
+    while (*output >= len && (val != 0 || len == 0)) {
       buf[len++] = '0' - (val % 10);
       val /= 10;
     }
     buf[len++] = '-';
   } else {
-    while (*output > len && (val != 0 || len == 0)) {
+    while (*output >= len && (val != 0 || len == 0)) {
       buf[len++] = '0' + (val % 10);
       val /= 10;
     }