In 1940 he was made a member of the Swedish Academy, and he also became an honorary doctor of philosophy at Lund University (1944).

A poem from Gullberg's book Kärlek i tjugonde seklet from 1933, called "Förklädd gud" ("God in disguise"), was set to music by the composer Lars-Erik Larsson in 1940.

The resulting lyrical suite has become one of the most well-recognised and best loved pieces of Swedish music for choir and orchestra.

[1] Gullberg had been suffering from myasthenia gravis, which resulted during his last few years that he was bound to his bed.

He committed suicide on 19 July 1961 by drowning at Lake Yddingen in Scania.