I've reproduced your crash. The issue is that you're using define within a nested REPL, which isn't supported [1]. However, a segfault is really not acceptable

I've reproduced your crash. The issue is that you're using define within a nested REPL, which isn't supported [1]. However, a segfault is really not acceptable. I'll file a report for this. [1] http://www.iro.umontreal.ca/~gambit/doc/gambit-c.html#Debugging http://www.iro.umontreal.ca/~gambit/doc/gambit-c.html#Debugg... Relevant section: "Note that some special forms (define in particular) can only be evaluated in the global interaction environment."