--- a/mercurial/revlog.py	Sun Dec 30 22:46:54 2018 -0500
+++ b/mercurial/revlog.py	Sun Dec 30 16:14:42 2018 +0100
@@ -1538,6 +1538,8 @@
         deltap = self.deltaparent(rev)
         if deltap == nullrev:
             return True
+        elif not self._sparserevlog:
+            return False
         p1, p2 = self.parentrevs(rev)
         if deltap in (p1, p2):
             return False