diff --git a/target/sparc/translate.c b/target/sparc/translate.c
index 655060cd9ac85ed0164a1c903ae0675ad567e1b6..aa6734d54e8f06e6a4efc93bf87f7fa63a070ad2 100644
--- a/target/sparc/translate.c
+++ b/target/sparc/translate.c
@@ -2448,8 +2448,31 @@ static void gen_ldstub_asi(DisasContext *dc, TCGv dst, TCGv addr, int insn)
         gen_ldstub(dc, dst, addr, da.mem_idx);
         break;
     default:
-        /* ??? Should be DAE_invalid_asi.  */
-        gen_exception(dc, TT_DATA_ACCESS);
+        /* ??? In theory, this should be raise DAE_invalid_asi.
+           But the SS-20 roms do ldstuba [%l0] #ASI_M_CTL, %o1.  */
+        if (parallel_cpus) {
+            gen_helper_exit_atomic(cpu_env);
+        } else {
+            TCGv_i32 r_asi = tcg_const_i32(da.asi);
+            TCGv_i32 r_mop = tcg_const_i32(MO_UB);
+            TCGv_i64 s64, t64;
+
+            save_state(dc);
+            t64 = tcg_temp_new_i64();
+            gen_helper_ld_asi(t64, cpu_env, addr, r_asi, r_mop);
+
+            s64 = tcg_const_i64(0xff);
+            gen_helper_st_asi(cpu_env, addr, s64, r_asi, r_mop);
+            tcg_temp_free_i64(s64);
+            tcg_temp_free_i32(r_mop);
+            tcg_temp_free_i32(r_asi);
+
+            tcg_gen_trunc_i64_tl(dst, t64);
+            tcg_temp_free_i64(t64);
+
+            /* End the TB.  */
+            dc->npc = DYNAMIC_PC;
+        }
         break;
     }
 }