Metabolite-binding riboswitches undergo structural changes to regulate transcription or translation of downstream genes. Two papers now identify a riboswitch in a non-coding small RNA (sRNA) that coordinates the expression of the ethanolamine utilization (eut) locus with the availability of essential cofactors of this pathway. DebRoy et al. showed that, in Enterococcus faecalis, the sRNA eutX, which is encoded by an intergenic region of the eut operon, inhibits eut gene expression by sequestering a positive regulator of actively transcribed eut mRNAs, termed EutV. Binding of the cofactor adenosyl cobalamine to the eutX riboswitch led to premature termination of eutX and truncated eutX transcripts that cannot bind EutV. Similarly, Mellin et al. report that full-length rli55 sRNA transcripts encoded by the eut locus sequester EutV in Listeria monocytogenes. Following binding of the cofactor vitamin B12 to the rli55 riboswitch, truncated rli55 transcripts are generated, which enables EutV to drive gene expression. Together, these studies provide evidence for a new class of riboswitch that ensures the appropriate activation of a metabolic pathway only in the presence of essential cofactors.