diff --git a/packages/backend/src/server/api/index.ts b/packages/backend/src/server/api/index.ts
index aa65077430..4eb87a6145 100644
--- a/packages/backend/src/server/api/index.ts
+++ b/packages/backend/src/server/api/index.ts
@@ -30,7 +30,7 @@ export enum IdType {
 export function convertId(idIn: string, idConvertTo: IdType ) {
 	let idArray = []
 	switch (idConvertTo) {
-		case IdType.CalckeyId:
+		case IdType.MastodonId:
 			idArray = [...idIn].map(item => item.charCodeAt(0));
 			idArray = idArray.map(item => {
 				if (item.toString().length < 3) {
@@ -39,8 +39,11 @@ export function convertId(idIn: string, idConvertTo: IdType ) {
 				else return item.toString()
 			});
 			return idArray.join('');
-		case IdType.MastodonId:
+		case IdType.CalckeyId:
 			for (let i = 0; i < idIn.length; i += 3) {
+				if ((idIn.length % 3) !== 0) {
+					idIn = `0${idIn}`
+				}
 				idArray.push(idIn.slice(i, i+3));
 			}
 			idArray = idArray.map(item => String.fromCharCode(item));