diff --git a/devel-requirements.txt b/devel-requirements.txt
index 6fee5e8e..02c7c88a 100644
--- a/devel-requirements.txt
+++ b/devel-requirements.txt
@@ -1,2 +1,2 @@
-pytest>=2.6
-Sphinx>=1.2.2
+pytest~=5.0
+Sphinx~=2.0
diff --git a/tox.ini b/tox.ini
index 341732df..df953c9c 100644
--- a/tox.ini
+++ b/tox.ini
@@ -22,8 +22,8 @@ setenv    =
 
 [testenv:docs-py3]
 basepython = python3.6
-deps       = sphinx
-             sphinx_rtd_theme
+deps       = sphinx~=2.0
+             sphinx_rtd_theme~=0.4
 changedir  = {toxinidir}/doc
 commands   = sphinx-build -W -b html -d {envtmpdir}/doctrees .  {envtmpdir}/html