What grammatical elements of a substrate language find their way into a creole? Grammatical features of the Oceanic substrate languages have been shown to be crucial in the development of Solomon Islands Pijin and of Melanesian Pidgin as a whole (Keesing 1988), so one might expect constructions which are very stable in the Oceanic family of languages to show up as substrate influence in the creole. This paper investigates three constructions in Oceanic languages which have been stable over thousands of years and persist throughout a majority of the Oceanic languages spoken in the Solomon Islands. The paper asks whether these are the sorts of constructions which could be expected to be reflected in Solomon Islands Pijin and shows that none of these persistent constructions appears in Solomon Islands Pijin at all. The absence of these constructions in Solomon Islands Pijin could be due to simplification: Creole genesis involves simplification of the substrate grammars. However, while simplification could be the explanation, it is not necessarily the case that all complex structures become simplified. For instance Solomon Islands Pijin pronoun paradigms are more complex than those in English, but the complexity is similar to that of the substrate languages. Thus it is not the case that all areas of a creole language are necessarily simplified. One must therefore look further than just simplification for an explanation of the presence or absence of stable grammatical features deriving from the substrate in creole languages. An account based on constraints in specific domains (Siegel 1999) is a better predictor of the behaviour of substrate constructions in Solomon Islands Pijin.