diff --git a/cpp/pyproject.toml.jinja b/cpp/pyproject.toml.jinja
index 5509239..c5155ac 100644
--- a/cpp/pyproject.toml.jinja
+++ b/cpp/pyproject.toml.jinja
@@ -44,6 +44,7 @@ develop = [
     "hatchling",
     "mdformat>=0.7.22,<1.1",
     "mdformat-tables>=1",
+    "pybind11",
     "pytest",
     "pytest-cov",
     "ruff>=0.9,<0.15",
diff --git a/cppjswasm/pyproject.toml.jinja b/cppjswasm/pyproject.toml.jinja
index 3450999..f0f6d0f 100644
--- a/cppjswasm/pyproject.toml.jinja
+++ b/cppjswasm/pyproject.toml.jinja
@@ -45,6 +45,7 @@ develop = [
     "hatch-cpp<0.3",
     "hatch-js",
     "hatchling",
+    "pybind11",
     "mdformat>=0.7.22,<1.1",
     "mdformat-tables>=1",
     "pytest",