nmslib: Optimized index raises RuntimeError on load when saved with `negdotprod` space

Basically, this is what I am trying to do

import nmslib

space = 'negdotprod'

vectors = [[1, 2], [3, 4], [5, 6]]

index = nmslib.init(space=space, method='hnsw')
index.addDataPointBatch(vectors)
index.createIndex(
    {'M': 15, 'efConstruction': 200, 'skip_optimized_index': 0, 'post': 0}
)
index.saveIndex('test.index')

new_index = nmslib.init(space=space, method='hnsw')
new_index.loadIndex('test.index')

and it raises

Check failed: totalElementsStored_ == this->data_.size() The number of stored elements 3 doesn't match the number of data points ! Did you forget to re-load data?
Traceback (most recent call last):
  File "8.py", line 15, in <module>
    new_index.loadIndex('test.index')
RuntimeError: Check failed: The number of stored elements 3 doesn't match the number of data points ! Did you forget to re-load data?

If I change space variable to cosinesimil, it works just fine. It seems that data points are not stored, even though hnsw method with skip_optimized_index=0 is used.