diff --git a/keyserver/src/user/login.js b/keyserver/src/user/login.js
--- a/keyserver/src/user/login.js
+++ b/keyserver/src/user/login.js
@@ -154,6 +154,19 @@
       return identity_info;
     } catch (err) {
       console.warn('Failed to register user: ' + getMessageForException(err));
+      if (userInfo.usingIdentityCredentials) {
+        if (process.env.NODE_ENV === 'development') {
+          console.warn(
+            'Please re-enter `nix develop` and provide new user credentials',
+          );
+        } else {
+          console.warn(
+            '\nFor keyservers running in Docker, set different ' +
+              'user credentials in COMM_JSONCONFIG_secrets_user_credentials, ' +
+              'remove all tables from the database, and restart',
+          );
+        }
+      }
       throw new ServerError('identity_auth_failed');
     }
   }