diff --git a/include/pocketpy/interpreter/vm.h b/include/pocketpy/interpreter/vm.h
index 2d800c82..678cdd20 100644
--- a/include/pocketpy/interpreter/vm.h
+++ b/include/pocketpy/interpreter/vm.h
@@ -28,7 +28,7 @@ typedef struct VM {
 
     py_TValue last_retval;
     py_TValue curr_exception;
-    bool is_signal_interrupted;
+    volatile bool is_signal_interrupted;
     bool is_curr_exc_handled;  // handled by try-except block but not cleared yet
 
     py_TValue reg[8];  // users' registers