diff --git a/util/sign.php b/util/sign.php
index b3c4110d..d0f8d3e8 100644
--- a/util/sign.php
+++ b/util/sign.php
@@ -128,27 +128,27 @@ function get_hash_values() {
 
    if($last_id == 0) {
       $start_id = TSA_START_ID;
-      if(MODE == 'unit') { $stop_id = $start_id + TSA_STAMP_REQUEST_UNIT_SIZE - 1; }
-      else { $stop_id = 1000000000; }
-   }
-   else {
+   } else {
       $start_id = $last_id + 1;
-      if(MODE == 'unit') { $stop_id = $start_id + TSA_STAMP_REQUEST_UNIT_SIZE - 1; }
-      else { $stop_id = 1000000000; }
    }
 
-   $query = $db->query("SELECT id, digest FROM " . TABLE_META . " WHERE id >= ? AND id <= ? ORDER BY id", array($start_id, $stop_id));
+   if(MODE == 'unit') {
+      $limit = TSA_STAMP_REQUEST_UNIT_SIZE;
+   } else {
+      $limit = 100000; // stay well below default PHP memory_limit
+   }
+
+   $query = $db->query("SELECT id, digest FROM " . TABLE_META . " WHERE id >= ? ORDER BY id LIMIT $limit", array($start_id));
 
    foreach($query->rows as $q) {
       $count++;
+      $last_id = $q['id'];
       $s .= $q['digest'];
    }
 
-   if(MODE == 'time') { $stop_id = $start_id + $count - 1; }
-
    return [
       START_ID => $start_id,
-      STOP_ID => $stop_id,
+      STOP_ID => $last_id,
       COUNT => $count,
       HASH_VALUE => hash(ALGO, $s)
    ];