diff --git a/build-aux/m4/calcdsl.m4 b/build-aux/m4/calcdsl.m4
index 50206f30..523549b7 100644
--- a/build-aux/m4/calcdsl.m4
+++ b/build-aux/m4/calcdsl.m4
@@ -91,7 +91,7 @@ AC_OUTPUT
 
 # we want this to run as part of the configure script, not during M4
 # expansion
-"$CALCROOT/build-aux/suppmk-gen" $SRCPATHS
+"$CALCROOT/build-aux/suppmk-gen" $SRCPATHS || exit
 
 AC_MSG_NOTICE([complete
 
diff --git a/build-aux/suppmk-gen b/build-aux/suppmk-gen
index 4cdf9931..67822e79 100755
--- a/build-aux/suppmk-gen
+++ b/build-aux/suppmk-gen
@@ -17,6 +17,8 @@
 #   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ##
 
+set -euo pipefail
+
 echo "Generating suppliers.mk..."
 # TODO: kluge; do properly.
 rm -f suppliers.mk