diff --git a/backend/src/graphql/resolver/BalanceResolver.ts b/backend/src/graphql/resolver/BalanceResolver.ts
index e067b4d68..902e50b8b 100644
--- a/backend/src/graphql/resolver/BalanceResolver.ts
+++ b/backend/src/graphql/resolver/BalanceResolver.ts
@@ -18,7 +18,8 @@ export class BalanceResolver {
     const balanceRepository = getCustomRepository(BalanceRepository)
     const userRepository = getCustomRepository(UserRepository)
 
-    const userEntity = await userRepository.findByPubkeyHex(context.pubKey)
+    const pubKeyString = Buffer.from(context.pubKey).toString('hex')
+    const userEntity = await userRepository.findByPubkeyHex(pubKeyString)
     const balanceEntity = await balanceRepository.findByUser(userEntity.id)
     const now = new Date()
 
diff --git a/backend/src/graphql/resolver/GdtResolver.ts b/backend/src/graphql/resolver/GdtResolver.ts
index b4f9a512b..ba10d45bf 100644
--- a/backend/src/graphql/resolver/GdtResolver.ts
+++ b/backend/src/graphql/resolver/GdtResolver.ts
@@ -22,7 +22,8 @@ export class GdtResolver {
   ): Promise<GdtEntryList> {
     // load user
     const userRepository = getCustomRepository(UserRepository)
-    const userEntity = await userRepository.findByPubkeyHex(context.pubKey)
+    const pubKeyString = Buffer.from(context.pubKey).toString('hex')
+    const userEntity = await userRepository.findByPubkeyHex(pubKeyString)
 
     const resultGDT = await apiGet(
       `${CONFIG.GDT_API_URL}/GdtEntries/listPerEmailApi/${userEntity.email}/${currentPage}/${pageSize}/${order}`,
diff --git a/backend/src/graphql/resolver/TransactionResolver.ts b/backend/src/graphql/resolver/TransactionResolver.ts
index 70dfdc505..b804c1af9 100644
--- a/backend/src/graphql/resolver/TransactionResolver.ts
+++ b/backend/src/graphql/resolver/TransactionResolver.ts
@@ -496,7 +496,8 @@ export class TransactionResolver {
   ): Promise<TransactionList> {
     // load user
     const userRepository = getCustomRepository(UserRepository)
-    const userEntity = await userRepository.findByPubkeyHex(context.pubKey)
+    const pubKeyString = Buffer.from(context.pubKey).toString('hex')
+    const userEntity = await userRepository.findByPubkeyHex(pubKeyString)
 
     const transactions = await listTransactions(currentPage, pageSize, order, userEntity)
 
@@ -531,7 +532,8 @@ export class TransactionResolver {
     // TODO this is subject to replay attacks
     // validate sender user (logged in)
     const userRepository = getCustomRepository(UserRepository)
-    const senderUser = await userRepository.findByPubkeyHex(context.pubKey)
+    const pubKeyString = Buffer.from(context.pubKey).toString('hex')
+    const senderUser = await userRepository.findByPubkeyHex(pubKeyString)
     if (senderUser.pubkey.length !== 32) {
       throw new Error('invalid sender public key')
     }