diff --git a/src/if_py_both.h b/src/if_py_both.h
index 0031003..5e12638 100644
--- a/src/if_py_both.h
+++ b/src/if_py_both.h
@@ -74,7 +74,7 @@
     static PyObject *
 OutputWrite(PyObject *self, PyObject *args)
 {
-    Py_ssize_t len;
+    Py_ssize_t len = 0;
     char *str = NULL;
     int error = ((OutputObject *)(self))->error;