The aim of the paper is to suggest ways of using poetry as a defossilizing force motivating students to reflect on grammar and its most problematic issues. Having presented learners' fossilized language competence in terms of grammar, involving examples of inaccuracies and/or understatements manifested by the advanced learners of Polish as a foreign language (146 students of the Polish Language Course attending the School of Polish Language and Culture at the University of Silesia in Katowice, Poland), suggestions for teachers of Polish as a foreign language and students themselves are offered. These include a few examples of activities based on poems believed to be perfect de-fossilizing teaching materials.