diff --git a/mercurial/parsers.c b/mercurial/parsers.c
--- a/mercurial/parsers.c
+++ b/mercurial/parsers.c
@@ -1232,6 +1232,7 @@ static PyObject *reachableroots(indexObj
 						if (val == NULL)
 							goto bail;
 						PySet_Add(reachable, val);
+						Py_DECREF(val);
 					}
 					Py_DECREF(p);
 				}