diff --git a/container-build/cerc-builder-js/build-npm-package-local-dependencies.sh b/container-build/cerc-builder-js/build-npm-package-local-dependencies.sh
index 3981e238..cb2b52a4 100755
--- a/container-build/cerc-builder-js/build-npm-package-local-dependencies.sh
+++ b/container-build/cerc-builder-js/build-npm-package-local-dependencies.sh
@@ -26,7 +26,7 @@ echo "Fixing up dependencies"
 for package in "${dependencies_from_scope[@]}"
 do
     echo "Fixing up package ${package}"
-    yarn-local-registry-fixup.sh $package
+    yarn-local-registry-fixup.sh $package ${local_npm_registry_url}
 done
 echo "Running build"
 build-npm-package.sh ${local_npm_registry_url} ${package_publish_version}
diff --git a/container-build/cerc-builder-js/yarn-local-registry-fixup.sh b/container-build/cerc-builder-js/yarn-local-registry-fixup.sh
index 13264a23..e6d9b793 100755
--- a/container-build/cerc-builder-js/yarn-local-registry-fixup.sh
+++ b/container-build/cerc-builder-js/yarn-local-registry-fixup.sh
@@ -1,5 +1,5 @@
 #!/bin/bash
-# Usage: yarn-local-registry-fixup.sh <package-to-fix>
+# Usage: yarn-local-registry-fixup.sh <package-to-fix> <registry-url>
 # Assumes package.json and yarn.lock are in the cwd
 # The purpose of this script is to take a project cloned from git
 # and "fixup" its yarn.lock file such that specified dependency
@@ -10,16 +10,24 @@
 if [ -n "$CERC_SCRIPT_DEBUG" ]; then
     set -x
 fi
-if [[ $# -ne 1 ]]; then
+if [[ $# -ne 2 ]]; then
     echo "Illegal number of parameters" >&2
     exit 1
 fi
 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 $versioned_target_package 2>/dev/null)
 # Code below parses out the values we need
 package_tarball=$(echo $yarn_info_output | jq -r .data.dist.tarball)
+# When running inside a container, the registry can return a URL with the wrong host name due to proxying
+# so we need to check if that has happened and fix the URL if so.
+if ! [[ "${package_tarball}" =~ ^${local_npm_registry_url}.* ]]; then
+    # HACK: I've hard-wired the host names below. Replace with proper implementation
+    package_tarball=$( echo ${package_tarball} | sed -e 's/localhost/host.docker.internal/g' )
+fi
 package_integrity=$(echo $yarn_info_output | jq -r .data.dist.integrity)
 package_shasum=$(echo $yarn_info_output | jq -r .data.dist.shasum)
 package_resolved=${package_tarball}#${package_shasum}
@@ -33,5 +41,6 @@ if [ -n "$CERC_SCRIPT_VERBOSE" ]; then
     echo "Resolved: ${package_resolved}"
 fi
 # Use magic sed regex to replace the values in yarn.lock
+# Note: yarn.lock is not json so we can not use jq for this
 sed -i -e '/^\"'${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