diff --git a/sklearn/_build_utils/__init__.py b/sklearn/_build_utils/__init__.py
index 0ed4968a1..91aa60f62 100644
--- a/sklearn/_build_utils/__init__.py
+++ b/sklearn/_build_utils/__init__.py
@@ -81,4 +81,4 @@ def maybe_cythonize_extensions(top_path, config):
             exc.args += (message,)
             raise
 
-        config.ext_modules = cythonize(config.ext_modules)
+        config.ext_modules = cythonize(config.ext_modules, nthreads=int(os.environ.get('JOBS', 1)))