Children with Specific Language Impairment (SLIC) experience difficulties in processing Subject relative clauses (SRC). This has been interpreted as evidence that they lack syntactic representations for SRC. Our study investigates the spontaneous production of SRC in typically developing children (TDC) and SLIC in a structural priming paradigm, and compares their performance in a sentence repetition task. We demonstrate that SLIC are much more likely to produce SRC during priming than in sentence repetition; moreover, when primed, their performance matches TDC's baseline (unprimed) performance. Furthermore, we design two simple unsupervised Bayesian models, and predict the developmental group (SLI, TD) and priming condition (Primed, Non-Primed). Overall, this study shows that SLIC can spontaneously produce SRC when primed, suggesting their impairment is related to working memory, rather than a deficit in syntactic knowledge.