diff --git a/examples/crbd.tppl b/examples/crbd.tppl
index 4b9b749..663a9b1 100644
--- a/examples/crbd.tppl
+++ b/examples/crbd.tppl
@@ -1,3 +1,7 @@
+import "treeppl::lib/trees.tppl"
+
+type alias Tree = ClockTree
+
 function simulateExtinctSubtree(time: Real, lambda: Real, mu: Real) {
   assume waitingTime ~ Exponential(lambda + mu);
   if waitingTime > time {
diff --git a/examples/treeppl_in_jupyter.ipynb b/examples/treeppl_in_jupyter.ipynb
index ff7e90b..13d26bc 100644
--- a/examples/treeppl_in_jupyter.ipynb
+++ b/examples/treeppl_in_jupyter.ipynb
@@ -227,6 +227,9 @@
    "outputs": [],
    "source": [
     "%%treeppl crbd -m smc-bpf --particles 10000 --resample align --subsample --subsample-size 10\n",
+    "import \"treeppl::lib/trees.tppl\"\n",
+    "\n",
+    "type alias Tree = ClockTree\n",
     "\n",
     "function simulateExtinctSubtree(time: Real, lambda: Real, mu: Real) {\n",
     "  assume waitingTime ~ Exponential(lambda + mu);\n",
diff --git a/tests/test_all.py b/tests/test_all.py
index 270442c..2aa240a 100644
--- a/tests/test_all.py
+++ b/tests/test_all.py
@@ -46,6 +46,10 @@ def test_tree_input():
     )
     with treeppl.Model(
         source="""\
+import "treeppl::lib/trees.tppl"
+
+type alias Tree = ClockTree
+
 function count_leaves(tree: Tree) => Int {
   if tree is Node {
     return count_leaves(tree.left) + count_leaves(tree.right);