diff --git a/.github/scripts/check-contrib.sh b/.github/scripts/check-contrib.sh
index f56a5a8a..3cc0ef32 100755
--- a/.github/scripts/check-contrib.sh
+++ b/.github/scripts/check-contrib.sh
@@ -1,5 +1,5 @@
 #!/usr/bin/env sh
-set -e
+set -eu
 
 bash --version
 zsh --version
diff --git a/contrib/coverage.bash b/contrib/coverage.bash
index fbf03fd4..b0c9ad29 100755
--- a/contrib/coverage.bash
+++ b/contrib/coverage.bash
@@ -1,5 +1,5 @@
 #!/usr/bin/env bash
-set -e
+set -eu
 
 usage() {
 	cat <<"EOF"