diff --git a/README.md b/README.md
index 6eb9de66843f192e3ea828914d78a20f89f9fb31..acbabdd2f00d38863bae70bf7debd991c545f4e0 100644
--- a/README.md
+++ b/README.md
@@ -113,6 +113,7 @@ Exception to this: the `http_logfile` option **ONLY** writes to local files.
 - `cookie_secret`: string. Authentication key for the session cookie. This can be a secret stored in a [vault](https://www.vaultproject.io/) using the form `/vault/path/key` e.g. `/vault/secret/cashier/cookie_secret`.
 - `csrf_secret`: string. Authentication key for CSRF protection. This can be a secret stored in a [vault](https://www.vaultproject.io/) using the form `/vault/path/key` e.g. `/vault/secret/cashier/csrf_secret`.
 - `http_logfile`: string. Path to the HTTP request log. Logs are written in the [Common Log Format](https://en.wikipedia.org/wiki/Common_Log_Format). The only valid destination for logs is a local file path.
+- `database`: See below.
 
 ### database
 
diff --git a/server/store/mem.go b/server/store/mem.go
index 68c5a13b4b38ef278b1fd67f790756ef28c7da90..c4fe14c0be3adea7e26322b34f5eb326c6bffdfb 100644
--- a/server/store/mem.go
+++ b/server/store/mem.go
@@ -2,6 +2,7 @@ package store
 
 import (
 	"fmt"
+	"log"
 	"sync"
 	"time"
 
@@ -94,6 +95,7 @@ func (ms *MemoryStore) clear() {
 
 // NewMemoryStore returns an in-memory CertStorer.
 func NewMemoryStore() *MemoryStore {
+	log.Println("WARNING: Using memory store to record issued certs.")
 	return &MemoryStore{
 		certs: make(map[string]*CertRecord),
 	}