diff --git a/target/arm/translate-a64.c b/target/arm/translate-a64.c
index b7b64f7358..163df8c615 100644
--- a/target/arm/translate-a64.c
+++ b/target/arm/translate-a64.c
@@ -3138,7 +3138,7 @@ static void disas_ldst_reg_imm9(DisasContext *s, uint32_t insn,
     bool is_store = false;
     bool is_extended = false;
     bool is_unpriv = (idx == 2);
-    bool iss_valid = !is_vector;
+    bool iss_valid;
     bool post_index;
     bool writeback;
     int memidx;
@@ -3191,6 +3191,8 @@ static void disas_ldst_reg_imm9(DisasContext *s, uint32_t insn,
         g_assert_not_reached();
     }
 
+    iss_valid = !is_vector && !writeback;
+
     if (rn == 31) {
         gen_check_sp_alignment(s);
     }