diff --git a/tree.go b/tree.go
index aba05a45..4493cf00 100644
--- a/tree.go
+++ b/tree.go
@@ -796,6 +796,9 @@ func (n *InternalNode) GetProofItems(keys keylist, resolver NodeResolverFn) (*Pr
 		if child != nil {
 			var c VerkleNode
 			if _, ok := child.(HashedNode); ok {
+				if resolver == nil {
+					return nil, nil, nil, fmt.Errorf("no resolver for path %x", keys[0][:n.depth+1])
+				}
 				serialized, err := resolver(keys[0][:n.depth+1])
 				if err != nil {
 					return nil, nil, nil, err