gistfile1.diff

diff --git a/vm/builtin/block_environment.cpp b/vm/builtin/block_environment.cpp
index d603156..ba93f94 100644
--- a/vm/builtin/block_environment.cpp
+++ b/vm/builtin/block_environment.cpp
@@ -149,6 +149,13 @@ namespace rubinius {
           if(!(ary = try_as<Array>(obj))) {
             if(CBOOL(obj->respond_to(state, G(sym_to_ary), cFalse))) {
               obj = obj->send(state, call_frame, G(sym_to_ary));
+              if(!obj) {
+                Exception* exc =
+                  as<Exception>(state->vm()->thread_state()->current_exception());
+                exc->locations(state, Location::from_call_stack(state, call_frame));
+                state->raise_exception(exc);
+                return NULL;
+              }
               if(!(ary = try_as<Array>(obj))) {
                 Exception::type_error(state, "to_ary must return an Array", call_frame);
                 return false;