diff --git a/etc/build.props b/etc/build.props
index 9ba4817..7249b1c 100644
--- a/etc/build.props
+++ b/etc/build.props
@@ -4,8 +4,8 @@ no_build = false
 requirements = \
   env:ISABELLE_SCALA_JAR
 sources = \
-  Isabelle_DOF/scala/dof.scala \
-  Isabelle_DOF/scala/dof_document_build.scala \
+  upstream_afp/Isabelle_DOF/scala/dof.scala \
+  upstream_afp/Isabelle_DOF/scala/dof_document_build.scala \
   scala/dof_mkroot.scala \
   scala/dof_tools.scala
 services = \