--- a/hgext3rd/evolve/cmdrewrite.py	Sat Mar 03 23:31:46 2018 +0530
+++ b/hgext3rd/evolve/cmdrewrite.py	Tue Mar 13 20:44:51 2018 +0530
@@ -1187,7 +1187,7 @@
 
             origctx = repo[revs.first()]
 
-            if origctx in pctx.ancestors():
+            if origctx in pctx.ancestors() or origctx.node() == pctx.node():
                 raise error.Abort(_("cannot grab an ancestor revision"))
 
             rewriteutil.precheck(repo, [origctx.rev()], 'grab')