The state Parole Board yesterday reversed its decision to free Jose Diaz, who gunned down beloved Bronx Assistant District Attorney Sean Healy in 1990, citing an incomplete parole record.

Thank goodness.

As The Post’s Murray Weiss first reported, the board hadn’t even heard testimony from Healy’s family — because Bronx DA Robert Johnson, Healy’s boss, neglected to tell them.

Indeed, Johnson’s office failed to show up at three straight parole hearings, starting in 2005. Which is simply baffling, given its clear interest in the case.

The result: A ruthless killer (Diaz shot Healy as he sprayed bullets at a bodega with an Uzi) nearly walked free after serving only 19 years.

Fortunately, Johnson’s office alerted the Parole Board and Healy’s family after it realized its oversight, leading to the board’s reconsideration.

But it was almost too late.

Let’s hope the Bronx DA stays more on top of things next time.