diff --git a/backend/src/graphql/resolver/TransactionLinkResolver.ts b/backend/src/graphql/resolver/TransactionLinkResolver.ts
index 79bfd375e..f831b7ff1 100644
--- a/backend/src/graphql/resolver/TransactionLinkResolver.ts
+++ b/backend/src/graphql/resolver/TransactionLinkResolver.ts
@@ -265,6 +265,7 @@ export class TransactionLinkResolver {
         const creations = await getUserCreation(user.id, clientTimezoneOffset)
         logger.info('open creations', creations)
         validateContribution(creations, contributionLink.amount, now, clientTimezoneOffset)
+
         const contribution = new DbContribution()
         contribution.userId = user.id
         contribution.createdAt = now
@@ -274,19 +275,16 @@ export class TransactionLinkResolver {
         contribution.contributionLinkId = contributionLink.id
         contribution.contributionType = ContributionType.LINK
         contribution.contributionStatus = ContributionStatus.CONFIRMED
-
         await queryRunner.manager.insert(DbContribution, contribution)
 
         const lastTransaction = await queryRunner.manager
           .createQueryBuilder()
           .select('transaction')
           .from(DbTransaction, 'transaction')
-          .innerJoinAndSelect('transaction.contribution', 'c')
           .where('transaction.userId = :id', { id: user.id })
           .orderBy('transaction.balanceDate', 'DESC')
           .getOne()
         let newBalance = new Decimal(0)
-
         let decay: Decay | null = null
         if (lastTransaction) {
           decay = calculateDecay(lastTransaction.balance, lastTransaction.balanceDate, now)
@@ -305,7 +303,6 @@ export class TransactionLinkResolver {
         transaction.balanceDate = now
         transaction.decay = decay ? decay.decay : new Decimal(0)
         transaction.decayStart = decay ? decay.start : null
-        transaction.contribution = contribution
         await queryRunner.manager.insert(DbTransaction, transaction)
 
         contribution.confirmedAt = now
diff --git a/backend/src/graphql/resolver/TransactionResolver.ts b/backend/src/graphql/resolver/TransactionResolver.ts
index 5fb13ba6b..7ec925181 100644
--- a/backend/src/graphql/resolver/TransactionResolver.ts
+++ b/backend/src/graphql/resolver/TransactionResolver.ts
@@ -206,7 +206,7 @@ export class TransactionResolver {
     // find current balance
     const lastTransaction = await dbTransaction.findOne(
       { userId: user.id },
-      { order: { balanceDate: 'DESC' } },
+      { order: { balanceDate: 'DESC' }, relations: ['contribution'] },
     )
     logger.debug(`lastTransaction=${lastTransaction}`)
 
@@ -313,6 +313,10 @@ export class TransactionResolver {
     @Ctx() context: Context,
   ): Promise<boolean> {
     logger.info(`sendCoins(email=${email}, amount=${amount}, memo=${memo})`)
+    if (amount.lte(0)) {
+      logger.error(`Amount to send must be positive`)
+      throw new Error('Amount to send must be positive')
+    }
 
     // TODO this is subject to replay attacks
     const senderUser = getUser(context)
diff --git a/backend/src/typeorm/repository/Transaction.ts b/backend/src/typeorm/repository/Transaction.ts
index 7952be0fc..943ad1081 100644
--- a/backend/src/typeorm/repository/Transaction.ts
+++ b/backend/src/typeorm/repository/Transaction.ts
@@ -15,7 +15,7 @@ export class TransactionRepository extends Repository<Transaction> {
   ): Promise<[Transaction[], number]> {
     if (onlyCreation) {
       return this.createQueryBuilder('userTransaction')
-        .innerJoinAndSelect(
+        .leftJoinAndSelect(
           'userTransaction.contribution',
           'c',
           'userTransaction.id = c.transactionId',
@@ -30,7 +30,7 @@ export class TransactionRepository extends Repository<Transaction> {
         .getManyAndCount()
     }
     return this.createQueryBuilder('userTransaction')
-      .innerJoinAndSelect(
+      .leftJoinAndSelect(
         'userTransaction.contribution',
         'c',
         'userTransaction.id = c.transactionId',
@@ -44,7 +44,7 @@ export class TransactionRepository extends Repository<Transaction> {
 
   findLastForUser(userId: number): Promise<Transaction | undefined> {
     return this.createQueryBuilder('userTransaction')
-      .innerJoinAndMapOne(
+      .leftJoinAndMapOne(
         'userTransaction.contribution',
         Contribution,
         'c',