diff --git a/tensorboard/pip_package/setup.py b/tensorboard/pip_package/setup.py
index <HASH>..<HASH> 100644
--- a/tensorboard/pip_package/setup.py
+++ b/tensorboard/pip_package/setup.py
@@ -64,6 +64,7 @@ setup(
     },
     install_requires=REQUIRED_PACKAGES,
     tests_require=REQUIRED_PACKAGES,
+    python_requires=">=3.6",
     # PyPI package information.
     classifiers=[
         "Development Status :: 4 - Beta",
pip: explicitly require Python <I> above (#<I>)

With `python_requires`, we can disallow other versions of Pythons from

installing TensorBoard. Removal in the earlier change was done without

completely understanding its intent.