diff --git a/examples/ext/lib_test/pyproject.toml b/examples/ext/lib_test/pyproject.toml
index 3691cdb..e747c6e 100644
--- a/examples/ext/lib_test/pyproject.toml
+++ b/examples/ext/lib_test/pyproject.toml
@@ -3,7 +3,10 @@
 # These requires are not effective yet, setup.cfg is.
 requires = [
     "setuptools >=39.2.0",
-    "wheel >= 0.35.1", ]
+    "wheel >= 0.35.1",
+    "pybind11 >= 2.6.2"
+]
+
 
 build-backend = "setuptools.build_meta"
 
diff --git a/examples/ext/lib_test/setup.cfg b/examples/ext/lib_test/setup.cfg
index 63f30ce..6d1ea15 100755
--- a/examples/ext/lib_test/setup.cfg
+++ b/examples/ext/lib_test/setup.cfg
@@ -34,6 +34,7 @@ install_requires =
 setup_requires =
     setuptools >=39.2.0
     wheel >= 0.35.1
+    pybind11 >= 2.6.2
 
 [options.extras_require]
 # To install these dependencies, run pip install .[test]