diff --git a/.tool-versions b/.tool-versions
index 220a35e7..f2a5a3f9 100644
--- a/.tool-versions
+++ b/.tool-versions
@@ -1,2 +1,2 @@
-elixir 1.6.4
-erlang 20.3
+elixir 1.6.6
+erlang 21.0
diff --git a/.travis.yml b/.travis.yml
index 7770bcad..4147fc7f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,10 +2,11 @@ language: elixir
 elixir:
   - 1.4.5
   - 1.5.3
-  - 1.6.4
+  - 1.6.6
 otp_release:
   - 19.3
   - 20.3
+  - 21.0
 
 before_script:
   - MIX_ENV=test mix compile --warnings-as-errors