diff --git a/src/lib-index/mail-index-private.h b/src/lib-index/mail-index-private.h
index b1a94a82c5..4350b1cfe5 100644
--- a/src/lib-index/mail-index-private.h
+++ b/src/lib-index/mail-index-private.h
@@ -338,8 +338,12 @@ void mail_index_view_transaction_unref(struct mail_index_view *view);
 
 void mail_index_fsck_locked(struct mail_index *index);
 
+/* Log an error and set it as the index's current error that is available
+   with mail_index_get_error_message(). */
 void mail_index_set_error(struct mail_index *index, const char *fmt, ...)
 	ATTR_FORMAT(2, 3);
+/* Same as mail_index_set_error(), but don't log the error. */
+void mail_index_set_error_nolog(struct mail_index *index, const char *str);
 /* "%s failed with index file %s: %m" */
 void mail_index_set_syscall_error(struct mail_index *index,
 				  const char *function);
diff --git a/src/lib-index/mail-index.c b/src/lib-index/mail-index.c
index 0c275e3b22..5f9e02a1c7 100644
--- a/src/lib-index/mail-index.c
+++ b/src/lib-index/mail-index.c
@@ -915,6 +915,15 @@ void mail_index_set_error(struct mail_index *index, const char *fmt, ...)
 	}
 }
 
+void mail_index_set_error_nolog(struct mail_index *index, const char *str)
+{
+	i_assert(str != NULL);
+
+	char *old_error = index->error;
+	index->error = i_strdup(str);
+	i_free(old_error);
+}
+
 bool mail_index_is_in_memory(struct mail_index *index)
 {
 	return MAIL_INDEX_IS_IN_MEMORY(index);