diff --git a/blockchain/pool_test.go b/blockchain/pool_test.go
index 0856a371..3e347fd2 100644
--- a/blockchain/pool_test.go
+++ b/blockchain/pool_test.go
@@ -23,7 +23,7 @@ func makePeers(numPeers int, minHeight, maxHeight int64) map[string]testPeer {
 	peers := make(map[string]testPeer, numPeers)
 	for i := 0; i < numPeers; i++ {
 		peerID := cmn.RandStr(12)
-		height := minHeight + int64(rand.Intn(int(maxHeight-minHeight)))
+		height := minHeight + rand.Int63n(maxHeight-minHeight)
 		peers[peerID] = testPeer{peerID, height}
 	}
 	return peers
diff --git a/rpc/core/blocks.go b/rpc/core/blocks.go
index a06ba83e..9d409845 100644
--- a/rpc/core/blocks.go
+++ b/rpc/core/blocks.go
@@ -74,9 +74,7 @@ func BlockchainInfo(minHeight, maxHeight int64) (*ctypes.ResultBlockchainInfo, e
 
 	// maximum 20 block metas
 	const limit int64 = 20
-	if maxHeight >= limit { // to prevent underflow
-		minHeight = cmn.MaxInt64(minHeight, maxHeight-limit)
-	}
+	minHeight = cmn.MaxInt64(minHeight, maxHeight-limit)
 
 	logger.Debug("BlockchainInfoHandler", "maxHeight", maxHeight, "minHeight", minHeight)
 
diff --git a/rpc/core/tx.go b/rpc/core/tx.go
index 0aa9f214..d0ff6840 100644
--- a/rpc/core/tx.go
+++ b/rpc/core/tx.go
@@ -88,8 +88,8 @@ func Tx(hash []byte, prove bool) (*ctypes.ResultTx, error) {
 
 	var proof types.TxProof
 	if prove {
-		// TODO: handle overflow
 		block := blockStore.LoadBlock(height)
+		// TODO: handle overflow
 		proof = block.Data.Txs.Proof(index)
 	}
 
@@ -187,8 +187,8 @@ func TxSearch(query string, prove bool) ([]*ctypes.ResultTx, error) {
 		index := r.Index
 
 		if prove {
-			// TODO: handle overflow
 			block := blockStore.LoadBlock(height)
+			// TODO: handle overflow
 			proof = block.Data.Txs.Proof(int(index))
 		}
 
diff --git a/types/validator_set.go b/types/validator_set.go
index cba9f206..134e4e06 100644
--- a/types/validator_set.go
+++ b/types/validator_set.go
@@ -53,7 +53,7 @@ func (valSet *ValidatorSet) IncrementAccum(times int) {
 	// Add VotingPower * times to each validator and order into heap.
 	validatorsHeap := cmn.NewHeap()
 	for _, val := range valSet.Validators {
-		val.Accum += int64(val.VotingPower) * int64(times) // TODO: mind overflow
+		val.Accum += val.VotingPower * int64(times) // TODO: mind overflow
 		validatorsHeap.Push(val, accumComparable{val})
 	}