--- a/src/plugins/fts-flatcurve/fts-backend-flatcurve-xapian.cc
+++ b/src/plugins/fts-flatcurve/fts-backend-flatcurve-xapian.cc
@@ -102,6 +102,7 @@
 #define FLATCURVE_DBW_LOCK_RETRY_SECS 1
 #define FLATCURVE_DBW_LOCK_RETRY_MAX 60
 #define FLATCURVE_MANUAL_OPTIMIZE_COMMIT_LIMIT 500
+#define FLATCURVE_OPTIMIZE_SKIP_LOG_LIMIT 10
 
 /* Lock: needed to ensure we don't run into race conditions when
  * manipulating current directory. */
@@ -1837,20 +1838,41 @@
 	Xapian::MSetIterator iter = mset.begin();
 
 	unsigned int updates = 0;
+	unsigned int skipped = 0;
 	for (iter = mset.begin(); iter != mset.end(); ++iter) {
-		Xapian::Document doc = iter.get_document();
 		try {
-	                xdb->dbw->replace_document(doc.get_docid(), doc);
+			Xapian::Document doc = iter.get_document();
+			xdb->dbw->replace_document(doc.get_docid(), doc);
 			if (++updates > FLATCURVE_MANUAL_OPTIMIZE_COMMIT_LIMIT) {
 				xdb->dbw->commit();
 				updates = 0;
 			}
-	        } catch (Xapian::Error &e) {
+		} catch (Xapian::DocNotFoundError &e) {
+			/* Document is in the MSet but its termlist cannot be
+			   read. Skip it rather than abandon the rebuild, which
+			   would leave every shard in place. Usually the message
+			   is already gone, but corruption looks the same here,
+			   so log it -- capped, since there may be many. */
+			if (skipped < FLATCURVE_OPTIMIZE_SKIP_LOG_LIMIT)
+				e_warning(backend->event, "Optimize: skipping "
+					  "unreadable document; %s",
+					  e.get_description().c_str());
+			++skipped;
+			/* commit() is inside the try, so the throw may arrive
+			   with documents counted but not committed. */
+			updates = 0;
+			continue;
+		} catch (Xapian::Error &e) {
 			*error_r = t_strdup(e.get_description().c_str());
 			return -1;
 		}
 	}
 
+	if (skipped > 0)
+		e_warning(backend->event, "Optimize: skipped %u unreadable "
+			  "document(s); reindex needed if the messages still "
+			  "exist", skipped);
+
 	return fts_flatcurve_xapian_close_db(
 			backend, xdb, FLATCURVE_XAPIAN_DB_CLOSE_WDB, error_r);
 }