Index: main/core/src/main/java/hudson/scm/CVSSCM.java
===================================================================
--- main/core/src/main/java/hudson/scm/CVSSCM.java	(revision 13571)
+++ main/core/src/main/java/hudson/scm/CVSSCM.java	(working copy)
@@ -766,7 +766,8 @@
                     task.setFailOnError(true);
                     BufferedOutputStream bufferedOutput = new BufferedOutputStream(out);
                     task.setDeststream(bufferedOutput);
-                    task.setBranch(branch);
+                    if(!isTag)
+                      task.setBranch(branch);
                     task.setStart(startTime);
                     task.setEnd(endTime);
                     if(changedFiles!=null) {