diff --git a/hgext/convert/common.py b/hgext/convert/common.py
--- a/hgext/convert/common.py
+++ b/hgext/convert/common.py
@@ -260,6 +260,11 @@ class converter_sink(object):
         """
         pass
 
+    def hascommitfrommap(self, rev):
+        """Return False if a rev mentioned in a filemap is known to not be
+        present."""
+        raise NotImplementedError
+
     def hascommitforsplicemap(self, rev):
         """This method is for the special needs for splicemap handling and not
         for general use. Returns True if the sink contains rev, aborts on some
diff --git a/hgext/convert/hg.py b/hgext/convert/hg.py
--- a/hgext/convert/hg.py
+++ b/hgext/convert/hg.py
@@ -253,6 +253,10 @@ class mercurial_sink(converter_sink):
             destmarks[bookmark] = bin(updatedbookmark[bookmark])
         destmarks.write()
 
+    def hascommitfrommap(self, rev):
+        # the exact semantics of clonebranches is unclear so we can't say no
+        return rev in self.repo or self.clonebranches
+
     def hascommitforsplicemap(self, rev):
         if rev not in self.repo and self.clonebranches:
             raise util.Abort(_('revision %s not found in destination '
diff --git a/hgext/convert/subversion.py b/hgext/convert/subversion.py
--- a/hgext/convert/subversion.py
+++ b/hgext/convert/subversion.py
@@ -1300,6 +1300,11 @@ class svn_sink(converter_sink, commandli
         self.ui.warn(_('writing Subversion tags is not yet implemented\n'))
         return None, None
 
+    def hascommitfrommap(self, rev):
+        # We trust that revisions referenced in a map still is present
+        # TODO: implement something better if necessary and feasible
+        return True
+
     def hascommitforsplicemap(self, rev):
         # This is not correct as one can convert to an existing subversion
         # repository and childmap would not list all revisions. Too bad.