Innovation patents were introduced into the Australian patents regime in 2001 and are proving to be largely immune from validity challenges. In a recent decision, the Full Federal Court upheld the validity of a patent claim relating to a process for rigidifying coal tailings. The key issue was the construction of the term ‘rigidification’ and whether it was distinct from a settling or sedimentation process. Justices Bennett and Finn answered this question in the affirmative, and found that: (i) the invention therefore varied from the prior art; and (ii) the variation made a substantive contribution to the working of the invention. On this basis, the patent claim satisfied the test of “innovative step”. Justice Dowsett dissented. Significantly, none of the Full Court judges found the expert evidence to be helpful in construing the term “rigidification” and their focus was solely on the wording of the patent specification – an explanation contained in the “summary of invention”, distinguishing the invention from the process of settling and sedimentation and underlining its importance, was considered persuasive by the Full Court majority, providing a helpful drafting tip for innovation patents.