diff --git a/target/xtensa/exc_helper.c b/target/xtensa/exc_helper.c
index d4823a65cd..43f6a862de 100644
--- a/target/xtensa/exc_helper.c
+++ b/target/xtensa/exc_helper.c
@@ -169,6 +169,9 @@ static void handle_interrupt(CPUXtensaState *env)
         CPUState *cs = env_cpu(env);
 
         if (level > 1) {
+            /* env->config->nlevel check should have ensured this */
+            assert(level < sizeof(env->config->interrupt_vector));
+
             env->sregs[EPC1 + level - 1] = env->pc;
             env->sregs[EPS2 + level - 2] = env->sregs[PS];
             env->sregs[PS] =