diff --git a/target/hppa/mem_helper.c b/target/hppa/mem_helper.c
index 4c28c58ee9..1387f4a64b 100644
--- a/target/hppa/mem_helper.c
+++ b/target/hppa/mem_helper.c
@@ -341,7 +341,7 @@ raise_exception_with_ior(CPUHPPAState *env, int excp, uintptr_t retaddr,
 
                 cpu_restore_state(cs, retaddr);
 
-                b = env->gr[env->unwind_breg];
+                b = env->unwind_breg ? env->gr[env->unwind_breg] : 0;
                 b >>= (env->psw & PSW_W ? 62 : 30);
                 env->cr[CR_IOR] |= b << 62;