diff --git a/CHANGELOG.md b/CHANGELOG.md
index f53a6543..b5f5ad4c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.16.4] - 2024-03-14
+### Fixed
+- [#216] Tree Exporter: Fix nan checker when printing trees.
+
 ## [0.16.3] - 2024-03-14
 ### Added
 - BaseNode: Add diameter property.
@@ -507,7 +511,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Utility Iterator: Tree traversal methods.
 - Workflow To Do App: Tree use case with to-do list implementation.
 
-[Unreleased]: https://github.com/kayjan/bigtree/compare/0.16.3...HEAD
+[Unreleased]: https://github.com/kayjan/bigtree/compare/0.16.4...HEAD
+[0.16.4]: https://github.com/kayjan/bigtree/compare/0.16.3...0.16.4
 [0.16.3]: https://github.com/kayjan/bigtree/compare/0.16.2...0.16.3
 [0.16.2]: https://github.com/kayjan/bigtree/compare/0.16.1...0.16.2
 [0.16.1]: https://github.com/kayjan/bigtree/compare/0.16.0...0.16.1
diff --git a/bigtree/__init__.py b/bigtree/__init__.py
index c438f1ea..9960d6bf 100644
--- a/bigtree/__init__.py
+++ b/bigtree/__init__.py
@@ -1,4 +1,4 @@
-__version__ = "0.16.3"
+__version__ = "0.16.4"
 
 from bigtree.binarytree.construct import list_to_binarytree
 from bigtree.dag.construct import dataframe_to_dag, dict_to_dag, list_to_dag
diff --git a/bigtree/tree/export.py b/bigtree/tree/export.py
index 7a281880..21f78c7a 100644
--- a/bigtree/tree/export.py
+++ b/bigtree/tree/export.py
@@ -60,7 +60,7 @@ def _isnull(value: Any) -> bool:
     Returns:
         (bool)
     """
-    if not value or math.isnan(value):
+    if not value or (isinstance(value, float) and math.isnan(value)):
         return True
     return False
 
diff --git a/docs/contributing.md b/docs/contributing.md
index 391aa8d7..7a6f563f 100644
--- a/docs/contributing.md
+++ b/docs/contributing.md
@@ -83,9 +83,7 @@ When creating branches, it is recommended to create them in the format `type/act
 $ git checkout -b feat/add-this
 ```
 
-When performing commits, it is also recommended to follow [conventional commits](https://www.conventionalcommits.org/en/v1.0.0/) when writing commit messages.
-
-During pre-commit checks, this project checks and formats code using `black`, `flake8`, `isort`, and `mypy`.
+During pre-commit checks, this project enforces [conventional commits](https://www.conventionalcommits.org/en/v1.0.0/) when writing commit messages, and checks and formats code using `black`, `flake8`, `isort`, and `mypy`.
 
 For testing, this project uses `pytest` and `coverage` package for testing of codes, and `docstr-coverage` and `doctest` package for testing of docstrings.
 
diff --git a/tests/tree/conftest.py b/tests/tree/conftest.py
index fc7b55f2..b78f10df 100644
--- a/tests/tree/conftest.py
+++ b/tests/tree/conftest.py
@@ -94,7 +94,7 @@ def tree_node_negative_null_attr():
     d = Node("d", age=1)
     e = Node("e", age=None)
     f = Node("f", age=float("nan"))
-    g = Node("g")
+    g = Node("g", age="10")
     h = Node("h")
 
     b.parent = a
diff --git a/tests/tree/test_export.py b/tests/tree/test_export.py
index 81e08dde..c7556ea2 100644
--- a/tests/tree/test_export.py
+++ b/tests/tree/test_export.py
@@ -97,7 +97,7 @@ def test_print_tree_attr_omit_null_false(tree_node_negative_null_attr):
             "├── b [age=-1]\n"
             "│   ├── d [age=1]\n"
             "│   └── e [age=None]\n"
-            "│       ├── g\n"
+            "│       ├── g [age=10]\n"
             "│       └── h\n"
             "└── c [age=0]\n"
             "    └── f [age=nan]\n"
@@ -117,7 +117,7 @@ def test_print_tree_attr_omit_null_true(tree_node_negative_null_attr):
             "├── b [age=-1]\n"
             "│   ├── d [age=1]\n"
             "│   └── e\n"
-            "│       ├── g\n"
+            "│       ├── g [age=10]\n"
             "│       └── h\n"
             "└── c\n"
             "    └── f\n"