diff --git a/docs/requirements.txt b/docs/requirements.txt
index 0900b94..3803fac 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -5,4 +5,4 @@ astropy>=1.3
 pandas>=0.20.1
 docopt>=0.6.2
          
-numpydoc
\ No newline at end of file
+numpydoc==0.8.0
\ No newline at end of file
diff --git a/test-requirements.txt b/test-requirements.txt
index 1ed5fae..4da57e2 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -1,11 +1,11 @@
 # add pytest plugins
-pytest-pep8
-pytest-cov
+pytest-pep8==1.0.6
+pytest-cov==2.5.1
 
 # to push results to codecov.io
-codecov
+codecov==2.0.15
 
 # for linting tests
-pylint
-pycodestyle
-pydocstyle
\ No newline at end of file
+pylint==1.9.1
+pycodestyle==2.4.0
+pydocstyle==2.1.1
\ No newline at end of file