diff --git a/.circleci/config.yml b/.circleci/config.yml
index cfb7bade0..6e49396af 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -3,6 +3,8 @@ version: 2
 
 jobs:
   test:
+    # Whenever the Go version is updated here, .travis.yml should also be
+    # updated.
     docker:
     - image: circleci/golang:1.10
     working_directory: /go/src/github.com/prometheus/prometheus
diff --git a/.travis.yml b/.travis.yml
index 82c5f11f2..7aacb0429 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,9 +2,10 @@ sudo: false
 
 language: go
 
+# Whenever the Go version is updated here, .circleci/config.yml should also be
+# updated.
 go:
 - 1.10.x
-- 1.x
 
 go_import_path: github.com/prometheus/prometheus