diff --git a/ci/install.sh b/ci/install.sh
index 9a896b90da..20bdd50918 100644
--- a/ci/install.sh
+++ b/ci/install.sh
@@ -10,6 +10,6 @@ main() {
     chmod +x qemu/qemu-system-arm
 }
 
-if [ $TRAVIS_BRANCH != master ] || [ $TRAVIS_PULL_REQUEST = true ]; then
+if [ $TRAVIS_BRANCH != master ] || [ $TRAVIS_PULL_REQUEST != false ]; then
     main
 fi
diff --git a/ci/script.sh b/ci/script.sh
index 7502b85028..5fc3ca2380 100644
--- a/ci/script.sh
+++ b/ci/script.sh
@@ -90,6 +90,6 @@ if [ -z ${TRAVIS_RUST_VERSION-} ]; then
     esac
 fi
 
-if [ $TRAVIS_BRANCH != master ] || [ $TRAVIS_PULL_REQUEST = true ]; then
+if [ $TRAVIS_BRANCH != master ] || [ $TRAVIS_PULL_REQUEST != false ]; then
     main
 fi