diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index aedb0d533..4902da3e9 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -7,7 +7,7 @@ Since last release
 
 **Added:**
 * Added package parameter to storage (#603, #612, #616)
-* Added package parameter to source (#613, #617, #621)
+* Added package parameter to source (#613, #617, #621, #623)
 * Added default keep packaging to reactor (#618, #619)
 
 **Changed:**
diff --git a/src/source.cc b/src/source.cc
index 751aaa763..4ffc3f560 100644
--- a/src/source.cc
+++ b/src/source.cc
@@ -54,20 +54,25 @@ std::string Source::str() {
 }
 
 void Source::EnterNotify() {
+  cyclus::Facility::EnterNotify();
+  RecordPosition();
+}
+
+void Source::Build(cyclus::Agent* parent) {
+  Facility::Build(parent);
+
   using cyclus::CompMap;
   using cyclus::Composition;
   using cyclus::Material;
-  cyclus::Facility::EnterNotify();
-  RecordPosition();
 
   // create all source inventory and place into buf
   cyclus::Material::Ptr all_inv;
   Composition::Ptr blank_comp = Composition::CreateFromMass(CompMap());
-
   all_inv = (outrecipe.empty() || context() == NULL) ? \
           Material::Create(this, inventory_size, blank_comp) : \
           Material::Create(this, inventory_size, context()->GetRecipe(outrecipe));
   inventory.Push(all_inv);
+
 }
 
 std::set<cyclus::BidPortfolio<cyclus::Material>::Ptr> Source::GetMatlBids(
diff --git a/src/source.h b/src/source.h
index 0024f20f4..db179d93a 100644
--- a/src/source.h
+++ b/src/source.h
@@ -71,6 +71,10 @@ class Source : public cyclus::Facility,
 
   virtual void EnterNotify();
 
+  /// --- Facility Members ---
+  /// perform module-specific tasks when entering the simulation
+  virtual void Build(cyclus::Agent* parent);
+
   virtual void GetMatlTrades(
     const std::vector< cyclus::Trade<cyclus::Material> >& trades,
     std::vector<std::pair<cyclus::Trade<cyclus::Material>,
diff --git a/src/source_tests.cc b/src/source_tests.cc
index 10208e733..d2ea3ec2b 100644
--- a/src/source_tests.cc
+++ b/src/source_tests.cc
@@ -15,7 +15,7 @@ void SourceTest::SetUp() {
   trader = tc.trader();
   InitParameters();
   SetUpSource();
-  src_facility->EnterNotify();
+  src_facility->Build(NULL);
 }
 
 void SourceTest::TearDown() {