diff --git a/ci/travis/travis_install.sh b/ci/travis/travis_install.sh
index 75e05886..111b114f 100644
--- a/ci/travis/travis_install.sh
+++ b/ci/travis/travis_install.sh
@@ -2,6 +2,11 @@
 
 set -ev
 
+# RVM overrides the cd, popd, and pushd shell commands, causing the
+# "shell_session_update: command not found" error on macOS when executing those
+# commands.
+unset -f cd popd pushd
+
 ####################
 # OS-specific setup
 ####################