diff --git a/cascading-pr.sh b/cascading-pr.sh
index 7794919..09a6aa6 100755
--- a/cascading-pr.sh
+++ b/cascading-pr.sh
@@ -2,6 +2,7 @@
 # SPDX-License-Identifier: MIT
 
 set -e
+set -o posix
 
 SELF=${BASH_SOURCE[0]}
 SELF_DIR="$( cd "$( dirname "$SELF" )" && pwd )"
diff --git a/tests/run.sh b/tests/run.sh
index 02a24ff..45dff2a 100755
--- a/tests/run.sh
+++ b/tests/run.sh
@@ -2,6 +2,7 @@
 # SPDX-License-Identifier: MIT
 
 set -e
+set -o posix
 
 SELF_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 TMPDIR=/tmp/cascading-pr-test