diff --git a/requirements.txt b/requirements.txt
index 48feb9a..2a40486 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,6 +1,6 @@
-numpy
-matplotlib
-astropy
-scipy
-pyastronomy
+numpy==1.15.0
+matplotlib==2.2.2
+astropy==3.0.4
+scipy==1.1.0
+pyastronomy==0.13.0
 
diff --git a/requirements_dev.txt b/requirements_dev.txt
index ee2c149..bab76c8 100644
--- a/requirements_dev.txt
+++ b/requirements_dev.txt
@@ -1,6 +1,6 @@
-hypothesis
-pytest
-pytest-cov
-python-coveralls
-codeclimate-test-reporter
-codacy-coverage
+hypothesis==3.66.30
+pytest==3.7.1
+pytest-cov==2.5.1
+python-coveralls==2.9.1
+codeclimate-test-reporter==0.2.3
+codacy-coverage==1.3.11