diff --git a/macros.pyproject b/macros.pyproject
index d615c22..bab2c4c 100644
--- a/macros.pyproject
+++ b/macros.pyproject
@@ -61,7 +61,7 @@ echo 'python3dist(toml)'
 # setuptools assumes no pre-existing dist-info
 rm -rfv *.dist-info/ >&2
 if [ -f %{__python3} ]; then
-  RPM_TOXENV="%{toxenv}" %{__python3} -I %{_rpmconfigdir}/redhat/pyproject_buildrequires.py %{?**}
+  RPM_TOXENV="%{toxenv}" HOSTNAME="rpmbuild" %{__python3} -I %{_rpmconfigdir}/redhat/pyproject_buildrequires.py %{?**}
 fi
 }
 
@@ -70,5 +70,6 @@ fi
 TOX_TESTENV_PASSENV="${TOX_TESTENV_PASSENV:-*}" \\
 PATH="%{buildroot}%{_bindir}:$PATH" \\
 PYTHONPATH="${PYTHONPATH:-%{buildroot}%{python3_sitearch}:%{buildroot}%{python3_sitelib}}" \\
+HOSTNAME="rpmbuild" \\
 tox --current-env -q --recreate -e "%{-e:%{-e*}}%{!-e:%{toxenv}}" %{?*}
 }
diff --git a/pyproject-rpm-macros.spec b/pyproject-rpm-macros.spec
index 3fdd306..fe8f52d 100644
--- a/pyproject-rpm-macros.spec
+++ b/pyproject-rpm-macros.spec
@@ -6,7 +6,7 @@ License:        MIT
 
 # Keep the version at zero and increment only release
 Version:        0
-Release:        16%{?dist}
+Release:        17%{?dist}
 
 # Macro files
 Source001:      macros.pyproject
@@ -87,6 +87,7 @@ install -m 644 pyproject_save_files.py  %{buildroot}%{_rpmconfigdir}/redhat/
 
 %if %{with tests}
 %check
+export HOSTNAME="rpmbuild"  # to speedup tox in network-less mock, see rhbz#1856356
 %{python3} -m pytest -vv --doctest-modules
 %endif
 
@@ -100,6 +101,10 @@ install -m 644 pyproject_save_files.py  %{buildroot}%{_rpmconfigdir}/redhat/
 %license LICENSE
 
 %changelog
+* Wed Jul 15 2020 Miro Hrončok <mhroncok@redhat.com> - 0-17
+- Set HOSTNAME to prevent tox 3.17+ from a DNS query
+- Fixes rhbz#1856356
+
 * Fri Jun 19 2020 Miro Hrončok <mhroncok@redhat.com> - 0-16
 - Switch from upstream deprecated pytoml to toml