In C the type char* usually represents a string, but it can also represent a generic pointer to memory. You have to tell the Gambit Scheme compiler what your intention is, so that it knows how to convert Scheme strings to that type. So instead of (pointer char) you have to use nonnull-char-string . Your array of strings is also terminated by NULL, so you need to say that too. This is the type nonnull-char-string-list . Use that instead of (pointer (pointer char) #f) .

Marc

Brilliant. That fixed it. Thanks very much.

Rob.