diff --git a/Modules/pyexpat.c b/Modules/pyexpat.c
index 01ac14ee6cd..07b1348d378 100644
--- a/Modules/pyexpat.c
+++ b/Modules/pyexpat.c
@@ -1503,7 +1503,9 @@ xmlparse_setattro(xmlparseobject *self, PyObject *name, PyObject *v)
       if (self->buffer != NULL) {
         /* there is already a buffer */
         if (self->buffer_used != 0) {
-          flush_character_buffer(self);
+            if (flush_character_buffer(self) < 0) {
+                return -1;
+            }
         }
         /* free existing buffer */
         free(self->buffer);