diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index b7e11f8..74bb262 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -679,7 +679,7 @@
 static PyObject *
 ImportError_str(PyImportErrorObject *self)
 {
-    if (self->msg) {
+    if (self->msg && PyUnicode_CheckExact(self->msg)) {
         Py_INCREF(self->msg);
         return self->msg;
     }