The present study aims to determine whether semantic relatedness plays a role in the production of speech errors involving derivational morphemes. A word order competition technique was used to induce morpheme and syllable exchange errors. Semantic relatedness was manipulated by contrasting error rates for prefixed words derived from free stems to those derived from bound roots. Significantly more morpheme errors were elicited in the two prefixed conditions compared with the control condition, replicating prior findings in French. Crucially, the two prefixed conditions elicited equal numbers of morpheme errors and there was no correlation between semantic relatedness and error rates. Taken together, the results strongly support a model of speech production in which derivational morphemes are represented at the form level and are not influenced by the degree of semantic relatedness within a morphological family.