diff --git a/.buildbot/p9.sh b/.buildbot/p9.sh
index 93b2c59..a014d3c 100644
--- a/.buildbot/p9.sh
+++ b/.buildbot/p9.sh
@@ -1,10 +1,14 @@
 #!/bin/bash
 
+# Exit on error:
+set -e
+
 # Check for required env variables ONNF_DEP_DIR, LLVM_PROJECT_ROOT
 if [[ -z "${ONNF_DEP_DIR}" ]]; then
   echo "ONNF_DEP_DIR env var is missing."
   exit 1
 fi
+
 if [[ -z "${LLVM_PROJECT_ROOT}" ]]; then
   echo "LLVM_PROJECT_ROOT env var is missing."
   exit 1
diff --git a/.buildbot/z13.sh b/.buildbot/z13.sh
index e027970..412224a 100644
--- a/.buildbot/z13.sh
+++ b/.buildbot/z13.sh
@@ -1,11 +1,19 @@
 #!/bin/bash
 
+# Exit on error:
+set -e
+
 # Check for required env variables JAVA_HOME
 if [[ -z "${JAVA_HOME}" ]]; then
   echo "JAVA_HOME env var is missing."
   exit 1
 fi
 
+if [[ -z "${LLVM_PROJECT_ROOT}" ]]; then
+  echo "LLVM_PROJECT_ROOT env var is missing."
+  exit 1
+fi
+
 # Set up mock installation path:
 export INSTALL_PATH=$WORKSPACE/INSTALL_PATH
 mkdir -p $INSTALL_PATH
@@ -22,13 +30,13 @@ export BUILD_PATH=$(pwd)
 export CPATH=$(pwd)/../runtime/
 
 mkdir build && cd build
-cmake -DCMAKE_C_COMPILER=$CC \
-      -DCMAKE_CXX_COMPILER=$CXX \
-      -DCMAKE_VERBOSE_MAKEFILE=ON \
-      -DCMAKE_INSTALL_PREFIX=$INSTALL_PATH \
-      -DONNF_ENABLE_NODE_TEST_JAVA=ON \
-      -DONNF_ENABLE_NODE_TEST_JNI=ON \
-      -DONNF_ENABLE_NODE_TEST_CPP=OFF \
+cmake -DCMAKE_C_COMPILER=$CC                  \
+      -DCMAKE_CXX_COMPILER=$CXX               \
+      -DCMAKE_VERBOSE_MAKEFILE=ON             \
+      -DCMAKE_INSTALL_PREFIX=$INSTALL_PATH    \
+      -DONNF_ENABLE_NODE_TEST_JAVA=ON         \
+      -DONNF_ENABLE_NODE_TEST_JNI=ON          \
+      -DONNF_ENABLE_NODE_TEST_CPP=OFF         \
       -DONNF_TARGET_ARCH=z13 ..
 
 make -j "$(nproc)" install