diff --git a/src/doc/rustc-dev-guide/.travis.yml b/src/doc/rustc-dev-guide/.travis.yml
index da9c1ed0aa1a..45ba4a890316 100644
--- a/src/doc/rustc-dev-guide/.travis.yml
+++ b/src/doc/rustc-dev-guide/.travis.yml
@@ -2,6 +2,7 @@ language: rust
 cache:
 - cargo
 before_install:
+- shopt -s globstar
 - MAX_LINE_LENGTH=80 bash ci/check_line_lengths.sh src/**/*.md
 install:
 - source ~/.cargo/env || true