diff --git a/core/embed/sys/syscall/stm32/syscall_dispatch.c b/core/embed/sys/syscall/stm32/syscall_dispatch.c
index e2bc1a6fba..62c21d6542 100644
--- a/core/embed/sys/syscall/stm32/syscall_dispatch.c
+++ b/core/embed/sys/syscall/stm32/syscall_dispatch.c
@@ -674,7 +674,7 @@ __attribute((no_stack_protector)) void syscall_handler(uint32_t *args,
     } break;
 
     default:
-      args[0] = 0xffffffff;
+      system_exit_fatal("Invalid syscall", __FILE__, __LINE__);
       break;
   }
 }