diff --git a/mercurial/dagop.py b/mercurial/dagop.py
--- a/mercurial/dagop.py
+++ b/mercurial/dagop.py
@@ -75,6 +75,23 @@ def _walkrevtree(pfunc, revs, startdepth
                 if prev != node.nullrev:
                     heapq.heappush(pendingheap, (heapsign * prev, pdepth))
 
+def filectxancestors(fctx, followfirst=False):
+    """Like filectx.ancestors()"""
+    visit = {}
+    c = fctx
+    if followfirst:
+        cut = 1
+    else:
+        cut = None
+
+    while True:
+        for parent in c.parents()[:cut]:
+            visit[(parent.linkrev(), parent.filenode())] = parent
+        if not visit:
+            break
+        c = visit.pop(max(visit))
+        yield c
+
 def _genrevancestors(repo, revs, followfirst, startdepth, stopdepth, cutfunc):
     if followfirst:
         cut = 1
diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -930,7 +930,8 @@ def _follow(repo, subset, x, name, follo
         s = set()
         for fname in files:
             fctx = c[fname]
-            s = s.union(set(c.rev() for c in fctx.ancestors(followfirst)))
+            a = dagop.filectxancestors(fctx, followfirst)
+            s = s.union(set(c.rev() for c in a))
             # include the revision responsible for the most recent version
             s.add(fctx.introrev())
     else: