The standard HPSG analysis of Germanic verb clusters can not explain the observed narrow-scope readings of adjuncts in such verb clusters. We present an extension of the HPSG analysis that accounts for the systematic ambiguity of the scope of adjuncts in verb cluster constructions, by treating adjuncts as members of the subcat list. The extension uses powerful recursive lexical rules, implemented as complex constraints. We show how `delayed evaluation' techniques from constraint-logic programming can be used to process such lexical rules.