diff --git a/domain/consensus/processes/blockbuilder/test_block_builder.go b/domain/consensus/processes/blockbuilder/test_block_builder.go
index 31eeea624..697672d60 100644
--- a/domain/consensus/processes/blockbuilder/test_block_builder.go
+++ b/domain/consensus/processes/blockbuilder/test_block_builder.go
@@ -28,6 +28,18 @@ func NewTestBlockBuilder(baseBlockBuilder model.BlockBuilder, testConsensus test
 	}
 }
 
+func cleanBlockPrefilledFields(block *externalapi.DomainBlock) {
+	for _, tx := range block.Transactions {
+		tx.Fee = 0
+		tx.Mass = 0
+		tx.ID = nil
+
+		for _, input := range tx.Inputs {
+			input.UTXOEntry = nil
+		}
+	}
+}
+
 // BuildBlockWithParents builds a block with provided parents, coinbaseData and transactions,
 // and returns the block together with its past UTXO-diff from the virtual.
 func (bb *testBlockBuilder) BuildBlockWithParents(parentHashes []*externalapi.DomainHash,
@@ -37,7 +49,16 @@ func (bb *testBlockBuilder) BuildBlockWithParents(parentHashes []*externalapi.Do
 	onEnd := logger.LogAndMeasureExecutionTime(log, "BuildBlockWithParents")
 	defer onEnd()
 
-	return bb.buildBlockWithParents(parentHashes, coinbaseData, transactions)
+	block, diff, err := bb.buildBlockWithParents(parentHashes, coinbaseData, transactions)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	// It's invalid to insert a block with prefilled fields to consensus, so we
+	// clean them before returning the block.
+	cleanBlockPrefilledFields(block)
+
+	return block, diff, nil
 }
 
 func (bb *testBlockBuilder) buildHeaderWithParents(parentHashes []*externalapi.DomainHash,
diff --git a/domain/consensus/processes/blockvalidator/block_body_in_isolation.go b/domain/consensus/processes/blockvalidator/block_body_in_isolation.go
index aa0f6d45c..4c3cf18d2 100644
--- a/domain/consensus/processes/blockvalidator/block_body_in_isolation.go
+++ b/domain/consensus/processes/blockvalidator/block_body_in_isolation.go
@@ -23,6 +23,11 @@ func (v *blockValidator) ValidateBodyInIsolation(blockHash *externalapi.DomainHa
 		return err
 	}
 
+	err = v.checkNoPrefilledFields(block)
+	if err != nil {
+		return err
+	}
+
 	err = v.checkBlockSize(block)
 	if err != nil {
 		return err
@@ -224,3 +229,28 @@ func (v *blockValidator) checkBlockSize(block *externalapi.DomainBlock) error {
 
 	return nil
 }
+
+func (v *blockValidator) checkNoPrefilledFields(block *externalapi.DomainBlock) error {
+	for _, tx := range block.Transactions {
+		if tx.Fee != 0 {
+			return errors.Errorf("transaction %s has a prefilled fee", consensushashing.TransactionID(tx))
+		}
+
+		if tx.Mass != 0 {
+			return errors.Errorf("transaction %s has a prefilled mass", consensushashing.TransactionID(tx))
+		}
+
+		if tx.ID != nil {
+			return errors.Errorf("transaction %s has a prefilled ID", consensushashing.TransactionID(tx))
+		}
+
+		for i, input := range tx.Inputs {
+			if input.UTXOEntry != nil {
+				return errors.Errorf("input %d in transaction %s has a prefilled UTXO entry",
+					i, consensushashing.TransactionID(tx))
+			}
+		}
+	}
+
+	return nil
+}
diff --git a/domain/consensus/test_consensus.go b/domain/consensus/test_consensus.go
index 8c4d002c6..c6e1809f6 100644
--- a/domain/consensus/test_consensus.go
+++ b/domain/consensus/test_consensus.go
@@ -30,7 +30,12 @@ func (tc *testConsensus) BuildBlockWithParents(parentHashes []*externalapi.Domai
 	tc.lock.Lock()
 	defer tc.lock.Unlock()
 
-	return tc.testBlockBuilder.BuildBlockWithParents(parentHashes, coinbaseData, transactions)
+	block, diff, err := tc.testBlockBuilder.BuildBlockWithParents(parentHashes, coinbaseData, transactions)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	return block, diff, nil
 }
 
 func (tc *testConsensus) AddBlock(parentHashes []*externalapi.DomainHash, coinbaseData *externalapi.DomainCoinbaseData,