diff --git a/target/arm/translate-a64.c b/target/arm/translate-a64.c
index 58ed4c6d05..113e2e172b 100644
--- a/target/arm/translate-a64.c
+++ b/target/arm/translate-a64.c
@@ -1913,7 +1913,7 @@ static void gen_store_exclusive(DisasContext *s, int rd, int rt, int rt2,
             tcg_gen_concat32_i64(val, cpu_exclusive_val, cpu_exclusive_high);
             tcg_gen_atomic_cmpxchg_i64(tmp, addr, val, tmp,
                                        get_mem_index(s),
-                                       size | MO_ALIGN | s->be_data);
+                                       MO_64 | MO_ALIGN | s->be_data);
             tcg_gen_setcond_i64(TCG_COND_NE, tmp, tmp, val);
             tcg_temp_free_i64(val);
         } else if (s->be_data == MO_LE) {