diff --git a/packages/web/src/Pages/SchemaUpdaterPage.php b/packages/web/src/Pages/SchemaUpdaterPage.php
index f8d2fec880..3541f3a33c 100644
--- a/packages/web/src/Pages/SchemaUpdaterPage.php
+++ b/packages/web/src/Pages/SchemaUpdaterPage.php
@@ -402,6 +402,9 @@ public function indexPost()
                         if (in_array($err, $skiperrs)) {
                             continue;
                         }
+                        if (self::_repairAndRetry($update, $err, $skiperrs)) {
+                            continue;
+                        }
                         $errors[] = sprintf(
                             "%s: %s\n",
                             _('Update ID'),
@@ -579,6 +582,48 @@ public function indexPost()
         }
         $this->jsonSend($code, $msg);
     }
+    /**
+     * Repair the structure and run the statement once more after a 1146.
+     *
+     * 1146 means the step names a table this database never got. Steps are
+     * positions, not identities, and 1.5.x fills the same positions with
+     * different migrations: 1.5.10.2518 arrives at 288, so 1.6's
+     * `CREATE TABLE fileDeleteQueue` (`// 287`) is skipped and `// 290`
+     * ALTERs a table that is not there. The reconcile after the loop creates
+     * it, but only once the update has already failed, so the installer
+     * printed "Failed!" and a second run was needed. This runs that repair at
+     * the point of failure instead.
+     *
+     * Any other error is left to the caller. So is a repair that does not
+     * succeed, and a retry that still fails: one repair, one retry.
+     *
+     * @param string        $update   the statement that failed
+     * @param int|string    $err      its MySQL error number
+     * @param array         $skiperrs the codes the updater tolerates
+     * @param callable|null $repair   SchemaReconciler::reconcile() unless given
+     *
+     * @return bool true when the statement now stands
+     */
+    private static function _repairAndRetry(
+        $update,
+        $err,
+        array $skiperrs,
+        $repair = null
+    ) {
+        if (1146 != $err) {
+            return false;
+        }
+        if (true !== call_user_func($repair ?: [SchemaReconciler::class, 'reconcile'])) {
+            // Leave the statement's own error behind for the caller to
+            // report, not whatever the repair ran last.
+            self::$DB->query($update);
+            return false;
+        }
+        if (false === self::$DB->query($update)->error) {
+            return true;
+        }
+        return in_array(self::$DB->errorCode, $skiperrs);
+    }
     /**
      * Drop NO_ZERO_DATE and NO_ZERO_IN_DATE from this session's sql_mode.
      *
diff --git a/tests/schema-updater-repairs-missing-table.test.php b/tests/schema-updater-repairs-missing-table.test.php
new file mode 100644
index 0000000000..b0e45491f4
--- /dev/null
+++ b/tests/schema-updater-repairs-missing-table.test.php
@@ -0,0 +1,118 @@
+<?php
+/**
+ * A step that names a table the database never got repairs and retries.
+ *
+ * `schemaVersion`.`vValue` is a count of applied array elements, and 1.5.x
+ * and 1.6 fill the same positions with different migrations (see
+ * SchemaReconciler's docblock). 1.5.10.2518 arrives at 288, so 1.6's steps
+ * `// 287` (CREATE TABLE fileDeleteQueue) and `// 288` are skipped and
+ * `// 290` ALTERs a table that is not there: error 1146. 1146 is not a
+ * tolerated code, so the update stopped, the reconcile after the loop then
+ * created the table, and the installer still printed "Failed!" with the
+ * server at 289. A second run went through -- after the admin had been told
+ * the one-way upgrade failed.
+ *
+ * SchemaUpdaterPage::_repairAndRetry() takes that second run's path inside
+ * the first: on 1146 it runs the repair (SchemaReconciler::reconcile() in
+ * production) and executes the same statement once more. These checks pin
+ * that, and pin that nothing else changes: any other error is left to the
+ * caller, a failed repair is not retried, and a retry that still fails is
+ * not retried again.
+ *
+ * No database: FogFakeDb plays the server and the repair is injected.
+ *
+ * Usage: php tests/schema-updater-repairs-missing-table.test.php
+ * Exit status 0 = pass, 1 = fail.
+ */
+
+require_once __DIR__ . '/lib/fog-test-harness.php';
+
+FogTestHarness::boot('schema-repair-retry');
+
+$t = new FogChecks();
+$db = FogTestHarness::fakeDb();
+
+$retry = new \ReflectionMethod('FOG\\Pages\\SchemaUpdaterPage', '_repairAndRetry');
+$retry->setAccessible(true);
+
+$skiperrs = [1050, 1054, 1060, 1061, 1062, 1091];
+$alter = 'ALTER TABLE `fileDeleteQueue` ADD `fdqPathType` VARCHAR(255) NOT NULL';
+
+/**
+ * Counters the closures below write into. An object rather than by-reference
+ * ints, so each check reads what the code under test actually did.
+ */
+$seen = new \stdClass();
+
+/**
+ * Answer $alter with $codes in turn (0 = success) and everything else with
+ * success. Resets the counters.
+ */
+$serve = static function (array $codes) use ($db, $alter, $seen) {
+    $seen->runs = 0;
+    $seen->repairs = 0;
+    $db->responder = static function ($sql) use ($db, $alter, &$codes, $seen) {
+        $code = 0;
+        if ($sql === $alter) {
+            $seen->runs++;
+            $code = $codes ? array_shift($codes) : 0;
+        }
+        $db->error = $code ? "error $code" : false;
+        $db->errorCode = $code ?: false;
+        return [];
+    };
+};
+
+$repairOk = static function () use ($seen) {
+    $seen->repairs++;
+    return true;
+};
+
+// --- 1146, the repair creates the table, the retry succeeds -----------------
+$serve([0]);
+$ok = $retry->invoke(null, $alter, 1146, $skiperrs, $repairOk);
+$t->check('1146: reported as handled', $ok === true);
+$t->check('1146: the repair ran once', $seen->repairs === 1);
+$t->check('1146: the statement ran again', $seen->runs === 1);
+
+// --- 1146, the retry hits a tolerated code (the repair added the column) ----
+$serve([1060]);
+$ok = $retry->invoke(null, $alter, 1146, $skiperrs, $repairOk);
+$t->check('1146 then 1060: handled like any tolerated duplicate', $ok === true);
+
+// --- 1146, the retry still fails --------------------------------------------
+$serve([1146]);
+$ok = $retry->invoke(null, $alter, 1146, $skiperrs, $repairOk);
+$t->check('1146 twice: left to the caller', $ok === false);
+$t->check('1146 twice: retried once, not looped', $seen->runs === 1 && $seen->repairs === 1);
+$t->check('1146 twice: the caller sees the statement\'s own error', $db->errorCode === 1146);
+
+// --- 1146, the repair itself fails ------------------------------------------
+$serve([1146]);
+$repairFails = static function () use ($seen) {
+    $seen->repairs++;
+    return 'reconcile failed';
+};
+$ok = $retry->invoke(null, $alter, 1146, $skiperrs, $repairFails);
+$t->check('failed repair: left to the caller', $ok === false);
+$t->check('failed repair: the caller sees the statement\'s own error', $db->errorCode === 1146);
+
+// --- any other error is not this method's business --------------------------
+foreach ([1064, 1452, 1005] as $code) {
+    $serve([]);
+        $ok = $retry->invoke(null, $alter, $code, $skiperrs, $repairOk);
+    $t->check("$code: left to the caller", $ok === false);
+    $t->check("$code: no repair, no retry", $seen->repairs === 0 && $seen->runs === 0);
+}
+
+// --- the production call site ------------------------------------------------
+$src = file_get_contents(dirname(__DIR__) . '/packages/web/src/Pages/SchemaUpdaterPage.php');
+$t->check(
+    'update() consults _repairAndRetry() after the tolerated codes',
+    (bool)preg_match(
+        '/in_array\(\$err, \$skiperrs\)\)\s*\{\s*continue;\s*\}\s*if \(self::_repairAndRetry\(\$update, \$err, \$skiperrs\)\)\s*\{\s*continue;\s*\}/',
+        $src
+    )
+);
+
+$t->finish();