The coumarin analogue WL12 is reported to efficiently inhibit JMJD6‐catalyzed histone N,N‐dimethylarginine demethylation, and cancer cell proliferation.[31,32] However, mass spectrometry (MS) assays indicated that WL12 does not inhibit JMJD6‐catalyzed lysyl‐residue hydroxylation.[31] Although Compound 7p is reported to efficiently and selectively inhibit isolated JMJD6,[33] the likely chemical and enzymatic instability of its 2,2,2‐trifluoroethyl ester substituent may limit its cellular and in vivo applications. Here, JMJD6 is linked to cancer.