diff --git a/.travis.yml b/.travis.yml
index 19942525..ae67b119 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -12,6 +12,7 @@ git:
 env:
   global:
     - GOOS=linux GOARCH=amd64
+    - GO111MODULE=on
     - GOLANGCI_VERSION="v1.14.0"
 
 matrix:
@@ -36,10 +37,17 @@ before_script:
   - ./cc-test-reporter before-build
 
 script:
+  # Ensure that the module files are being kept correctly and that vendored dependencies are up-to-date.
+  - go mod tidy
+  - go mod vendor
+  - git diff --exit-code --quiet || (echo "Please run 'go mod tidy' to clean up the 'go.mod' and 'go.sum' files."; false)
+
   # Run the linter.
   - golangci-lint run
+
   # Run all the tests with the race detector and generate coverage.
   - go test -v -race -coverprofile c.out ./...
+
   # Run the build script to generate the necessary binaries and images.
   - /bin/bash ci/bintray.sh
 
diff --git a/go.sum b/go.sum
index 57659c44..c14505b2 100644
--- a/go.sum
+++ b/go.sum
@@ -15,8 +15,6 @@ github.com/bwmarrin/discordgo v0.19.0/go.mod h1:O9S4p+ofTFwB02em7jkpkV8M3R0/PUVO
 github.com/coreos/etcd v3.3.10+incompatible/go.mod h1:uF7uidLiAD3TWHmW31ZFd/JWoc32PjwdhPthX9715RE=
 github.com/coreos/go-etcd v2.0.0+incompatible/go.mod h1:Jez6KQU2B/sWsbdaef3ED8NzMklzPG4d5KIOhIy30Tk=
 github.com/coreos/go-semver v0.2.0/go.mod h1:nnelYz7RCh+5ahJtPPxZlU+153eP4D4r3EedlOD2RNk=
-github.com/d5/tengo v1.9.2 h1:UE/X8PYl7bLS4Ww2zGeh91nq5PTnkhe8ncgNeA5PK7k=
-github.com/d5/tengo v1.9.2/go.mod h1:gsbjo7lBXzBIWBd6NQp1lRKqqiDDANqBOyhW8rTlFsY=
 github.com/d5/tengo v1.12.1 h1:libKkDM95CsZgYs6E5eiEaM9sbcw2EzJRSkr9o5NO4s=
 github.com/d5/tengo v1.12.1/go.mod h1:gsbjo7lBXzBIWBd6NQp1lRKqqiDDANqBOyhW8rTlFsY=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=