diff --git a/src/main/org/apache/tools/ant/types/defaults.properties b/src/main/org/apache/tools/ant/types/defaults.properties
index 23d2c5990..f52da372e 100644
--- a/src/main/org/apache/tools/ant/types/defaults.properties
+++ b/src/main/org/apache/tools/ant/types/defaults.properties
@@ -12,3 +12,5 @@ patternset=org.apache.tools.ant.types.PatternSet
 regexp=org.apache.tools.ant.types.RegularExpression
 substitution=org.apache.tools.ant.types.Substitution
 xmlcatalog=org.apache.tools.ant.types.XMLCatalog
+extensionSet=org.apache.tools.ant.taskdefs.optional.extension.ExtensionSet
+extension=org.apache.tools.ant.taskdefs.optional.extension.ExtensionAdapter
\ No newline at end of file