The `barThickness` option was missing in the definition file. See 03735563f4/src/controllers/controller.bar.js (L165) or 8e37a11e39/docs/04-Bar-Chart.md (chart-options)
03735563f4/src/controllers/controller.bar.js (L165)
8e37a11e39/docs/04-Bar-Chart.md (chart-options)
...must be "tooltips" (plurar) instead of "tooltip" in ChartOptions My custom callback given in "ChartTooltipOptions.custom" was never called... :/ "tooltips" (plurar) is OK Take a look @ http://www.chartjs.org/docs/#advanced-usage-external-tooltips