gdalinfo documentation includes -json flag but using it returns “FAILURE: Unknown option name '-json'”

Reading the documentation for gdalinfo describes the option of formatting the output as JSON.

-json

Display the output in json format.

However, when I use the -json tag it appears not to be implemented.

> gdalinfo -json translated_image_overlay.png
Usage: gdalinfo [--help-general] [-mm] [-stats] [-hist] [-nogcp] [-nomd]
                          [-norat] [-noct] [-nofl] [-checksum] [-proj4]
                          [-listmdd] [-mdd domain|all]*
                          [-sd subdataset] datasetname

FAILURE: Unknown option name ‘-json’

I have GDAL 1.11.1 installed.

Can someone explain why this is happening?