diff --git a/src/partcad/assembly.py b/src/partcad/assembly.py
index 4d506cb7..fd029ba2 100644
--- a/src/partcad/assembly.py
+++ b/src/partcad/assembly.py
@@ -45,12 +45,20 @@ def __init__(self, name=None, config={}):
         # TODO(clairbee): add reference counter to assemblies
         self.count = 0
 
+        self.instantiated = False
+
+    def do_instantiate(self):
+        if not self.instantiated:
+            self.instantiate(self)
+            self.instantiated = True
+
     def add(
         self,
         child_item: shape.Shape,  # pc.Part or pc.Assembly
         name=None,
         loc=b3d.Location((0.0, 0.0, 0.0), (0.0, 0.0, 1.0), 0.0),
     ):
+        # It's called from instantiate() only, so no need to do_instantiate()
         self.children.append(AssemblyChild(child_item, name, loc))
 
         # Keep part reference counter for bill-of-materials purposes
@@ -60,10 +68,12 @@ def add(
         self.shape = None
 
     def ref_inc(self):
+        self.do_instantiate()
         for child in self.children:
             child.item.ref_inc()
 
     def get_shape(self):
+        self.do_instantiate()
         if self.shape is None:
             child_shapes = []
             for child in self.children:
@@ -82,9 +92,11 @@ def get_shape(self):
         return copy.copy(self.shape)
 
     def _render_txt_real(self, file):
+        self.do_instantiate()
         for child in self.children:
             child._render_txt_real(file)
 
     def _render_markdown_real(self, file):
+        self.do_instantiate()
         for child in self.children:
             child._render_markdown_real(file)
diff --git a/src/partcad/assembly_factory.py b/src/partcad/assembly_factory.py
index baa0a30e..9be4dac9 100644
--- a/src/partcad/assembly_factory.py
+++ b/src/partcad/assembly_factory.py
@@ -32,6 +32,8 @@ def __init__(self, ctx, project, assembly_config, extension=""):
 
     def _create(self, assembly_config):
         self.assembly = assembly.Assembly(self.name, assembly_config)
-
-    def _save(self):
         self.project.assemblies[self.name] = self.assembly
+
+        self.assembly.instantiate = lambda assembly_self: self.instantiate(
+            assembly_self
+        )
diff --git a/src/partcad/assembly_factory_assy.py b/src/partcad/assembly_factory_assy.py
index b32b83d2..943e167c 100644
--- a/src/partcad/assembly_factory_assy.py
+++ b/src/partcad/assembly_factory_assy.py
@@ -23,6 +23,7 @@ def __init__(self, ctx, project, assembly_config):
         # Complement the config object here if necessary
         self._create(assembly_config)
 
+    def instantiate(self, assembly):
         self.assy = {}
         if os.path.exists(self.path):
             try:
@@ -35,9 +36,7 @@ def __init__(self, ctx, project, assembly_config):
             logging.error("ERROR: Assembly file not found: %s" % self.path)
 
         if "links" in self.assy and not self.assy["links"] is None:
-            self.handle_node_list(self.assembly, self.assy["links"])
-
-        self._save()
+            self.handle_node_list(assembly, self.assy["links"])
 
     def handle_node_list(self, assembly, node_list):
         for link in node_list:
@@ -62,6 +61,7 @@ def handle_node(self, assembly, node):
         # Check if this node is for an assembly
         if "links" in node:
             item = Assembly(name, node["links"])
+            item.instantiate = lambda x: True
             self.handle_node_list(item, node["links"])
         else:
             # This is a node for a part