diff --git a/src/comp/middle/trans.rs b/src/comp/middle/trans.rs
index 454a9429eede..ee31ae3e3569 100644
--- a/src/comp/middle/trans.rs
+++ b/src/comp/middle/trans.rs
@@ -4409,12 +4409,22 @@ fn trans_fail_expr(cx: &@block_ctxt, sp_opt: &option::t<span>,
         let e_ty = ty::expr_ty(tcx, expr);
         bcx = expr_res.bcx;
 
-
         if ty::type_is_str(tcx, e_ty) {
-            let elt =
-                GEP(bcx, expr_res.val,
-                              [C_int(0), C_int(abi::vec_elt_data)]);
-            ret trans_fail_value(bcx, sp_opt, elt);
+            let is_istr = alt ty::struct(tcx, e_ty) {
+              ty::ty_istr. { true }
+              _ { false }
+            };
+            if !is_istr {
+                let elt =
+                    GEP(bcx, expr_res.val,
+                        [C_int(0), C_int(abi::vec_elt_data)]);
+                ret trans_fail_value(bcx, sp_opt, elt);
+            } else {
+                let data = ivec::get_dataptr(
+                    bcx, expr_res.val,
+                    type_of_or_i8(bcx, ty::mk_mach(tcx, ast::ty_u8)));
+                ret trans_fail_value(bcx, sp_opt, data);
+            }
         } else {
             bcx_ccx(cx).sess.span_bug(expr.span,
                                       ~"fail called with unsupported type "
diff --git a/src/comp/middle/typeck.rs b/src/comp/middle/typeck.rs
index 74fff2e82bd6..c6e11bf722de 100644
--- a/src/comp/middle/typeck.rs
+++ b/src/comp/middle/typeck.rs
@@ -1860,7 +1860,15 @@ fn check_expr_with_unifier(fcx: &@fn_ctxt, expr: &@ast::expr, unify: &unifier,
         bot = true;
         alt expr_opt {
           none. {/* do nothing */ }
-          some(e) { check_expr_with(fcx, e, ty::mk_str(tcx)); }
+          some(e) {
+            // FIXME: istr transitional. Should be:
+            // check_expr_with(fcx, e, ty::mk_str(tcx));
+            check_expr(fcx, e);
+            if !are_compatible(fcx, expr_ty(tcx, e), ty::mk_str(tcx))
+                && !are_compatible(fcx, expr_ty(tcx, e), ty::mk_istr(tcx)) {
+                check_expr_with(fcx, e, ty::mk_str(tcx));
+            }
+          }
         }
         write::bot_ty(tcx, id);
       }
diff --git a/src/test/run-fail/explicit-fail-msg.rs b/src/test/run-fail/explicit-fail-msg.rs
index b45e443759c5..56937260b54e 100644
--- a/src/test/run-fail/explicit-fail-msg.rs
+++ b/src/test/run-fail/explicit-fail-msg.rs
@@ -1,3 +1,3 @@
 // error-pattern:wooooo
 // no-valgrind
-fn main() { let a = 1; if 1 == 1 { a = 2; } fail "woooo" + "o"; }
+fn main() { let a = 1; if 1 == 1 { a = 2; } fail ~"woooo" + ~"o"; }