diff --git a/core/trie/key.go b/core/trie/key.go
index 3101d51d14..db60754fb7 100644
--- a/core/trie/key.go
+++ b/core/trie/key.go
@@ -26,7 +26,7 @@ func NewKey(length uint8, keyBytes []byte) Key {
 
 func (k *Key) SubKey(n uint8) (*Key, error) {
 	if n > k.len {
-		return nil, errors.New(fmt.Sprint("cannot subtract key by len %i", n))
+		return nil, errors.New(fmt.Sprint("cannot subtract key of length %i from key of length %i", n, k.len))
 	}
 
 	newKey := &Key{len: n}
diff --git a/core/trie/proof.go b/core/trie/proof.go
index 4bceba5332..5da9fee7f8 100644
--- a/core/trie/proof.go
+++ b/core/trie/proof.go
@@ -122,9 +122,7 @@ func GetProof(key *Key, tri *Trie) ([]ProofNode, error) {
 
 	var parentKey *Key
 
-	for i := 0; i < len(nodesFromRoot); i++ {
-		sNode := nodesFromRoot[i]
-
+	for i, sNode := range nodesFromRoot {
 		sNodeEdge, sNodeBinary, err := transformNode(tri, parentKey, sNode)
 		if err != nil {
 			return nil, err