diff --git a/app/data/container-build/cerc-builder-js/build-npm-package-local-dependencies.sh b/app/data/container-build/cerc-builder-js/build-npm-package-local-dependencies.sh
index 2824e008..69e8e99e 100755
--- a/app/data/container-build/cerc-builder-js/build-npm-package-local-dependencies.sh
+++ b/app/data/container-build/cerc-builder-js/build-npm-package-local-dependencies.sh
@@ -13,6 +13,8 @@ if [[ -z "${CERC_NPM_AUTH_TOKEN}" ]]; then
     echo "CERC_NPM_AUTH_TOKEN is not set" >&2
     exit 1
 fi
+# Exit on error
+set -e
 local_npm_registry_url=$1
 package_publish_version=$2
 # TODO: make this a paramater and allow a list of scopes
diff --git a/app/data/container-build/cerc-builder-js/build-npm-package.sh b/app/data/container-build/cerc-builder-js/build-npm-package.sh
index 9c9ac580..490389a3 100755
--- a/app/data/container-build/cerc-builder-js/build-npm-package.sh
+++ b/app/data/container-build/cerc-builder-js/build-npm-package.sh
@@ -17,6 +17,8 @@ if [[ $# -eq 2 ]]; then
 else
     package_publish_version=$( cat package.json | jq -r .version )
 fi
+# Exit on error
+set -e
 # Get the name of this package from package.json since we weren't passed that
 package_name=$( cat package.json | jq -r .name )
 local_npm_registry_url=$1
diff --git a/app/data/container-build/cerc-builder-js/yarn-local-registry-fixup.sh b/app/data/container-build/cerc-builder-js/yarn-local-registry-fixup.sh
index 987fcbc2..3f4f095a 100755
--- a/app/data/container-build/cerc-builder-js/yarn-local-registry-fixup.sh
+++ b/app/data/container-build/cerc-builder-js/yarn-local-registry-fixup.sh
@@ -14,14 +14,23 @@ if [[ $# -ne 2 ]]; then
     echo "Illegal number of parameters" >&2
     exit 1
 fi
+# Exit on error
+set -e
 target_package=$1
 local_npm_registry_url=$2
 # TODO: use jq rather than sed here:
 versioned_target_package=$(grep ${target_package} package.json | sed -e 's#[[:space:]]\{1,\}\"\('${target_package}'\)\":[[:space:]]\{1,\}\"\(.*\)\",#\1@\2#' )
 # Use yarn info to get URL checksums etc from the new registry
 yarn_info_output=$(yarn info --json $versioned_target_package 2>/dev/null)
-# Code below parses out the values we need
+# First check if the target version actually exists. 
+# If it doesn't exist there will be no .data.dist.tarball element,
+# and jq will output the string "null"
 package_tarball=$(echo $yarn_info_output | jq -r .data.dist.tarball)
+if [[ $package_tarball == "null" ]]; then
+    echo "FATAL: Target package version ($versioned_target_package) not found" >&2
+    exit 1
+fi
+# Code below parses out the values we need
 # When running inside a container, the registry can return a URL with the wrong host name due to proxying
 # so we need to check if that has happened and fix the URL if so.
 if ! [[ "${package_tarball}" =~ ^${local_npm_registry_url}.* ]]; then
@@ -33,6 +42,7 @@ package_integrity=$(echo $yarn_info_output | jq -r .data.dist.integrity)
 package_shasum=$(echo $yarn_info_output | jq -r .data.dist.shasum)
 package_resolved=${package_tarball}#${package_shasum}
 # Some strings need to be escaped so they work when passed to sed later
+escaped_package_integrity=$(printf '%s\n' "$package_integrity" | sed -e 's/[\/&]/\\&/g')
 escaped_package_resolved=$(printf '%s\n' "$package_resolved" | sed -e 's/[\/&]/\\&/g')
 escaped_target_package=$(printf '%s\n' "$target_package" | sed -e 's/[\/&]/\\&/g')
 if [ -n "$CERC_SCRIPT_VERBOSE" ]; then
@@ -44,4 +54,4 @@ fi
 # Use magic sed regex to replace the values in yarn.lock
 # Note: yarn.lock is not json so we can not use jq for this
 sed -i -e '/^\"'${escaped_target_package}'.*\":$/ , /^\".*$/ s/^\([[:space:]]\{1,\}resolved \).*$/\1'\"${escaped_package_resolved}\"'/' yarn.lock
-sed -i -e '/^\"'${escaped_target_package}'.*\":$/ , /^\".*$/ s/^\([[:space:]]\{1,\}integrity \).*$/\1'${package_integrity}'/' yarn.lock
+sed -i -e '/^\"'${escaped_target_package}'.*\":$/ , /^\".*$/ s/^\([[:space:]]\{1,\}integrity \).*$/\1'${escaped_package_integrity}'/' yarn.lock
diff --git a/app/data/stacks/fixturenet-laconicd/stack.yml b/app/data/stacks/fixturenet-laconicd/stack.yml
index 1d059b52..fca9623f 100644
--- a/app/data/stacks/fixturenet-laconicd/stack.yml
+++ b/app/data/stacks/fixturenet-laconicd/stack.yml
@@ -1,5 +1,6 @@
 version: "1.0"
 name: fixturenet-laconicd
+description: "A laconicd fixturenet"
 repos:
   - cerc-io/laconicd
   - cerc-io/laconic-sdk