diff --git a/master/buildbot/steps/source/cvs.py b/master/buildbot/steps/source/cvs.py
index 359a8d3783a..83530fde287 100644
--- a/master/buildbot/steps/source/cvs.py
+++ b/master/buildbot/steps/source/cvs.py
@@ -177,7 +177,11 @@ def doCheckout(self, dir):
 
     def doUpdate(self):
         command = ['-z3', 'update', '-dP']
-        if self.branch:
+        branch = self.branch
+        # special case. 'cvs update -r HEAD -D today' gives no files; see #2351
+        if branch == 'HEAD' and self.revision:
+            branch = None
+        if branch:
             command += ['-r', self.branch]
         if self.revision:
             command += ['-D', self.revision]
diff --git a/master/buildbot/test/unit/test_steps_source_cvs.py b/master/buildbot/test/unit/test_steps_source_cvs.py
index 9622b28f302..9ec337f4de8 100644
--- a/master/buildbot/test/unit/test_steps_source_cvs.py
+++ b/master/buildbot/test/unit/test_steps_source_cvs.py
@@ -362,6 +362,36 @@ def test_mode_incremental_branch(self):
         self.expectOutcome(result=SUCCESS, status_text=["update"])
         return self.runStep()
 
+    def test_mode_incremental_special_case(self):
+        self.setupStep(
+            cvs.CVS(cvsroot=":pserver:anonymous@cvs-mirror.mozilla.org:/cvsroot",
+                    cvsmodule="mozilla/browser/", mode='incremental',
+                    branch='HEAD', login=True),
+            args=dict(revision='2012-08-16 16:05:16 +0000'))
+        self.expectCommands(
+            ExpectShell(workdir='wkdir',
+                        command=['cvs', '--version'])
+            + 0,
+            Expect('uploadFile', dict(blocksize=32768, maxsize=None,
+                        slavesrc='Root', workdir='wkdir/CVS',
+                        writer=ExpectRemoteRef(shell.StringFileWriter)))
+            + Expect.behavior(uploadString(':pserver:anonymous@cvs-mirror.mozilla.org:/cvsroot'))
+            + 0,
+            Expect('uploadFile', dict(blocksize=32768, maxsize=None,
+                        slavesrc='Repository', workdir='wkdir/CVS',
+                        writer=ExpectRemoteRef(shell.StringFileWriter)))
+            + Expect.behavior(uploadString('mozilla/browser/'))
+            + 0,
+            ExpectShell(workdir='wkdir',
+                command=['cvs', '-z3', 'update', '-dP',
+                            # note, no -r HEAD here - that's the special case
+                            '-D', '2012-08-16 16:05:16 +0000'])
+            + 0,
+            )
+
+        self.expectOutcome(result=SUCCESS, status_text=["update"])
+        return self.runStep()
+
     def test_mode_incremental_branch_sourcestamp(self):
         self.setupStep(
             cvs.CVS(cvsroot=":pserver:anonymous@cvs-mirror.mozilla.org:/cvsroot",