diff --git a/src/main/org/apache/tools/ant/taskdefs/defaults.properties b/src/main/org/apache/tools/ant/taskdefs/defaults.properties
index 5e2d978b3..960fd81cc 100644
--- a/src/main/org/apache/tools/ant/taskdefs/defaults.properties
+++ b/src/main/org/apache/tools/ant/taskdefs/defaults.properties
@@ -67,6 +67,7 @@ dirname=org.apache.tools.ant.taskdefs.Dirname
 cvschangelog=org.apache.tools.ant.taskdefs.cvslib.ChangeLogTask
 buildnumber=org.apache.tools.ant.taskdefs.BuildNumber
 concat=org.apache.tools.ant.taskdefs.Concat
+cvstagdiff=org.apache.tools.ant.taskdefs.cvslib.CvsTagDiff
 
 # optional tasks
 script=org.apache.tools.ant.taskdefs.optional.Script