--- a/hgsubversion/editor.py
+++ b/hgsubversion/editor.py
@@ -578,6 +578,12 @@ class HgEditor(svnwrap.Editor):
             try:
                 if not self.meta.is_path_valid(path):
                     return
+
+                # are we skipping this branch entirely?
+                br_path, branch = self.meta.split_branch_path(path)[:2]
+                if self.meta.skipbranch(branch):
+                    return
+
                 try:
                     handler(window)
                 except AssertionError, e: # pragma: no cover

--- a/hgsubversion/maps.py
+++ b/hgsubversion/maps.py
@@ -425,12 +425,7 @@ class BranchMap(dict):
             dst = dst.strip()
             self.meta.ui.debug('adding branch %s to branch map\n' % src)
 
-            if not dst:
-                # prevent people from assuming such lines are valid
-                raise hgutil.Abort('removing branches is not supported, yet\n'
-                                   '(line %i in branch map %s)'
-                                   % (number, path))
-            elif src in self and dst != self[src]:
+            if dst and src in self and dst != self[src]:
                 msg = 'overriding branch: "%s" to "%s" (%s)\n'
                 self.meta.ui.status(msg % (self[src], dst, src))
             self[src] = dst

--- a/hgsubversion/replay.py
+++ b/hgsubversion/replay.py
@@ -121,6 +121,12 @@ def _convert_rev(ui, meta, svn, r, tbdel
         if branch in current.emptybranches and files:
             del current.emptybranches[branch]
 
+        if meta.skipbranch(branch):
+            # make sure we also get rid of it from emptybranches
+            if branch in current.emptybranches:
+                del current.emptybranches[branch]
+            continue
+
         files = dict(files)
         parents = meta.get_parent_revision(rev.revnum, branch), revlog.nullid
         if parents[0] in closedrevs and branch in meta.closebranches:
@@ -195,6 +201,9 @@ def _convert_rev(ui, meta, svn, r, tbdel
     # 2. handle branches that need to be committed without any files
     for branch in current.emptybranches:
 
+        if meta.skipbranch(branch):
+            continue
+
         ha = meta.get_parent_revision(rev.revnum, branch)
         if ha == node.nullid:
             continue

--- a/hgsubversion/stupid.py
+++ b/hgsubversion/stupid.py
@@ -684,6 +684,10 @@ def convert_rev(ui, meta, svn, r, tbdelt
     date = meta.fixdate(r.date)
     check_deleted_branches = set(tbdelta['branches'][1])
     for b in branches:
+
+        if meta.skipbranch(b):
+            continue
+
         parentctx = meta.repo[meta.get_parent_revision(r.revnum, b)]
         tag = meta.get_path_tag(meta.remotename(b))
         kind = svn.checkpath(branches[b], r.revnum)

--- a/tests/test_fetch_mappings.py
+++ b/tests/test_fetch_mappings.py
@@ -290,6 +290,23 @@ class MapTests(test_util.TestBase):
         for r in repo:
             self.assertEquals(verify.verify(ui, repo, rev=r), 0)
 
+    def test_branchmap_no_replacement(self):
+        '''test that empty mappings are accepted
+
+        Empty mappings are lines like 'this ='. We check that such branches are
+        not converted.
+        '''
+        repo_path = self.load_svndump('branchmap.svndump')
+        branchmap = open(self.branchmap, 'w')
+        branchmap.write("badname =\n")
+        branchmap.close()
+        ui = self.ui()
+        ui.setconfig('hgsubversion', 'branchmap', self.branchmap)
+        commands.clone(ui, test_util.fileurl(repo_path),
+                       self.wc_path, branchmap=self.branchmap)
+        branches = set(self.repo[i].branch() for i in self.repo)
+        self.assertEquals(sorted(branches), ['default', 'feature'])
+
     def test_tagmap(self):
         repo_path = self.load_svndump('basic_tag_tests.svndump')
         tagmap = open(self.tagmap, 'w')