Testimony is a valuable source of information for young learners, in particular if children maintain vigilance against errors while still being open to learning from imperfectly knowledgeable sources. We find support for this idea by examining how children evaluate individual speakers who present very different epistemic risks by being previously ignorant or inaccurate. Results across 2 experiments show that children attribute knowledge to (Experiment 1) and endorse new claims made by speakers (Experiment 2) who previously professed ignorance about familiar object labels, but not to speakers whose labels were previously inaccurate. Study 2 further clarifies that children are not simply relying on links between informational access and knowledge; children rejected testimony from a previously inaccurate speaker even when she had perceptual access to support her claim. These results show that children actively monitor the reliability of a speaker's knowledge claims, distinguish unreliable speakers from those who sometimes admit ignorance, raising new questions about how such admissions factor in to children's appraisal of the scope and limits of a person's knowledge.