.

go/zodb/btree/btree.go

@@ -306,8 +306,8 @@ func (bt *btreeState) PySetState(pystate interface{}) (err error) {
 	if !ok {
 		return fmt.Errorf("data: expect (...); got %T", t[0])
 	}
-	if len(t) % 2 != 0 {
-		return fmt.Errorf("data: expect [%%2](); got [%d]()", len(t))
+	if len(t) % 2 == 0 {
+		return fmt.Errorf("data: expect [!%%2](); got [%d]()", len(t))
 	}
 
 	bt.firstbucket, ok = t[1].(*Bucket)
@@ -315,7 +315,7 @@ func (bt *btreeState) PySetState(pystate interface{}) (err error) {
 		return fmt.Errorf("first bucket: must be Bucket; got %T", t[1])
 	}
 
-	n := len(t) / 2
+	n := (len(t) + 1) / 2
 	bt.data = make([]zBTreeItem, 0, n)
 	for i, idx := 0, 0; i < n; i++ {
 		key := int64(0)