A controller includes an interface and a processor. The interface is configured to communicate with a nonvolatile memory including multiple memory cells organized in multiple memory blocks that each includes multiple Word Lines (WLs). The processor is configured to store first data in one or more WLs of a memory block, the first data occupies less than a maximal number of WLs available in the memory block, to calculate redundancy data over the first data and store the redundancy data in a dedicated memory, to program second data to a selected WL of the memory block that was not programmed with the first data, to check a programming status resulting from the programming of the selected WL, and in response to identifying that programming the second data to the selected WL has corrupted at least part of the first data, to recover the first data using the redundancy data.