diff --git a/environment.yml b/environment.yml
index 1a86a5c..df081a4 100644
--- a/environment.yml
+++ b/environment.yml
@@ -3,7 +3,6 @@ channels:
   - conda-forge
 dependencies:
   - python=3.6
-  - pyyaml=3.12
   - google-api-python-client=1.6.7
   - oauth2client=4.1.2
   - slackclient=1.2.1
@@ -13,6 +12,7 @@ dependencies:
   - pycodestyle=2.4.0 # Dev dependency.
   - pylint=1.9.2 # Dev dependency.
   - pip:
+      - pyyaml>=5.1
       - responses==0.10.2 # Dev dependency.
       - schedule==0.5.0
       - httplib2shim==0.0.3
diff --git a/requirements.txt b/requirements.txt
index 7c50a07..da8937a 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,5 +1,5 @@
 pyjwt==1.5.3
-pyyaml==3.12
+pyyaml>=5.1
 slackclient==1.2.1
 schedule==0.5.0
 google-api-python-client==1.6.7