diff --git a/pyproject.toml b/pyproject.toml
index 46a745e..3f479c3 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,5 +1,4 @@
 [build-system]
 requires = ["setuptools>=30.3.0",
-            "setuptools_scm",
-            "wheel"]
+            "setuptools_scm"]
 build-backend = "setuptools.build_meta"
diff --git a/tox.ini b/tox.ini
index 63d406c..5a33eef 100644
--- a/tox.ini
+++ b/tox.ini
@@ -5,13 +5,10 @@ envlist =
     twine
     bandit
     linkcheck
-requires =
-    setuptools >= 30.3.0
-    pip >= 19.3.1
 
 [testenv]
 setenv =
-    devdeps: PIP_EXTRA_INDEX_URL = https://pypi.anaconda.org/astropy/simple https://pypi.anaconda.org/scientific-python-nightly-wheels/simple
+    devdeps: PIP_EXTRA_INDEX_URL = https://pypi.anaconda.org/astropy/simple https://pypi.anaconda.org/liberfa/simple https://pypi.anaconda.org/scientific-python-nightly-wheels/simple
 
 # Pass through the following environemnt variables which are needed for the CI
 passenv = HOME,WINDIR,CI,PYSYN_CDBS
@@ -49,6 +46,7 @@ deps =
     # or nightly wheel of key dependencies.
     devdeps: numpy>=0.0.dev0
     devdeps: scipy>=0.0.dev0
+    devdeps: pyerfa>=0.0.dev0
     devdeps: astropy>=0.0.dev0
     devdeps: git+https://github.com/spacetelescope/synphot_refactor.git@master#egg=synphot