diff --git a/jenkins.sh b/jenkins.sh
index a421c4d27..c09239251 100755
--- a/jenkins.sh
+++ b/jenkins.sh
@@ -1,14 +1,27 @@
-#!/bin/bash -l
+#!/bin/bash
+
+set -e
+
 export NVM_DIR="/home/jenkins/.nvm"
 [ -s "$NVM_DIR/nvm.sh" ] && . "$NVM_DIR/nvm.sh"
 nvm use 4
+
+set -x
+
+# install the versions of js-sdk and react-sdk provided to us by jenkins
+npm install ./node_modules/matrix-js-sdk-*.tgz
+npm install ./node_modules/matrix-react-sdk-*.tgz
+
+# install the other dependencies
 npm install
-(cd node_modules/matrix-react-sdk && npm run build) # npm doesn't do this when dependencies point at github.com >:(
-npm run build # Dumps artificats to /vector
+
+# build our artifacts; dumps them in ./vector
+npm run build
 
 # gzip up ./vector
 rm vector-*.tar.gz || true # rm previous artifacts without failing if it doesn't exist
-REACT_SHA=$(grep 'gitHead' node_modules/matrix-react-sdk/package.json | cut -d \" -f 4 | head -c 12) # node_modules deps from 'npm install' don't have a .git dir so can't rev-parse.
-JSSDK_SHA=$(grep 'gitHead' node_modules/matrix-js-sdk/package.json | cut -d \" -f 4 | head -c 12)    # But they do set the commit in package.json under 'gitHead' which we're grabbing here.
+
+REACT_SHA=$(head -c 12 node_modules/matrix-react-sdk/version.txt)
+JSSDK_SHA=$(head -c 12 node_modules/matrix-js-sdk/version.txt)
 VECTOR_SHA=$(git rev-parse --short=12 HEAD) # use the ACTUAL SHA rather than assume develop
 tar -zcvhf vector-$VECTOR_SHA-react-$REACT_SHA-js-$JSSDK_SHA.tar.gz vector #g[z]ip, [c]reate archive, [v]erbose, [f]ilename, [h]ard-dereference (do not archive symlinks)