Index: setup.py
--- setup.py.orig
+++ setup.py
@@ -113,8 +113,8 @@ class CMakeBuild(build_ext):
         elif os.path.exists(os.path.join(BASEDIR, 'contrib', 'protozero', 'include', 'protozero', 'version.hpp')):
             cmake_args += ['-DPROTOZERO_INCLUDE_DIR={}/contrib/protozero/include'.format(BASEDIR)]
 
-        if 'PYBIND11_PREFIX' in env:
-            cmake_args += ['-DPYBIND11_PREFIX={}'.format(env['PYBIND11_PREFIX'])]
+        if 'pybind11_DIR' in env:
+            cmake_args += ['-Dpybind11_DIR={}'.format(env['pybind11_DIR'])]
         elif os.path.exists(os.path.join(BASEDIR, 'contrib', 'pybind11')):
             cmake_args += ['-DPYBIND11_PREFIX={}/contrib/pybind11'.format(BASEDIR)]