diff --git a/jenkins.sh b/jenkins.sh
index bfda843150..634703eb29 100755
--- a/jenkins.sh
+++ b/jenkins.sh
@@ -8,20 +8,23 @@ 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
 
+# we may be using a dev branch of react-sdk, in which case we need to build it
+(cd node_modules/matrix-react-sdk && npm run build)
+
 # 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=$(head -c 12 node_modules/matrix-react-sdk/git-revision.txt)
-JSSDK_SHA=$(head -c 12 node_modules/matrix-js-sdk/git-revision.txt)
+ # node_modules deps from 'npm install' don't have a .git dir so can't
+ # rev-parse; but they do set the commit in package.json under 'gitHead' which
+ # we're grabbing here.
+REACT_SHA=$(grep 'gitHead' node_modules/matrix-react-sdk/package.json | cut -d \" -f 4 | head -c 12)
+JSSDK_SHA=$(grep 'gitHead' node_modules/matrix-js-sdk/package.json | cut -d \" -f 4 | head -c 12)
+
 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)