diff --git a/lib/errors.js b/lib/errors.js
index bb9b4144..ace9e9fb 100644
--- a/lib/errors.js
+++ b/lib/errors.js
@@ -7,6 +7,12 @@ const SERVER_ERROR = 'SERVER_ERROR'
 
 // https://gist.github.com/derhuerst/79d49c0f04c1c192a5d15756e5af575f/edit
 const byErrorCode = Object.assign(Object.create(null), {
+	H_UNKNOWN: {
+		isServer: false,
+		code: SERVER_ERROR,
+		message: 'unknown internal error',
+		statusCode: 500,
+	},
 	AUTH: {
 		isClient: true,
 		code: ACCESS_DENIED,