diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index f3494bd..f80b8ff 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -113,8 +113,9 @@
 #### Initialization and command line parsing
 ################################################################
 
-# Abort on errors (and uninitialised variables)
-set -eu
+# Abort on errors (even on the left-hand side of a pipe).
+# Treat uninitialised variables as errors.
+set -e -o pipefail -u
 
 pre_check_environment () {
     if [ -d library -a -d include -a -d tests ]; then :; else