diff --git a/src/librustc/middle/trans/expr.rs b/src/librustc/middle/trans/expr.rs
index e1de66152069d..9a019f98a493c 100644
--- a/src/librustc/middle/trans/expr.rs
+++ b/src/librustc/middle/trans/expr.rs
@@ -1726,9 +1726,14 @@ fn trans_imm_cast(bcx: @mut Block, expr: &ast::Expr,
             (cast_enum, cast_float) => {
                 let bcx = bcx;
                 let repr = adt::represent_type(ccx, t_in);
-                let slot = Alloca(bcx, ll_t_in, "");
-                Store(bcx, llexpr, slot);
-                let lldiscrim_a = adt::trans_get_discr(bcx, repr, slot, Some(Type::i64()));
+                let llexpr_ptr;
+                if type_is_immediate(ccx, t_in) {
+                    llexpr_ptr = Alloca(bcx, ll_t_in, "");
+                    Store(bcx, llexpr, llexpr_ptr);
+                } else {
+                    llexpr_ptr = llexpr;
+                }
+                let lldiscrim_a = adt::trans_get_discr(bcx, repr, llexpr_ptr, Some(Type::i64()));
                 match k_out {
                     cast_integral => int_cast(bcx, ll_t_out,
                                               val_ty(lldiscrim_a),