The guilt of Ephraim is stored up. His sin is stored up.
Amazingly, the imagery is the same here as that of  Revelation 18:5, where the sins of the great harlot church are represented as a scroll long enough to reach heaven itself!  Again, we have a perfect correspondence between the sacred writers of the Old Testament and the New Testament. Both this verse, and the next one find their perfect echoes in the writings of the apostle John.  In the following verse, it is the conception of the new birth!