diff --git a/apps/update-sources/src/node-modules.ts b/apps/update-sources/src/node-modules.ts
index 0b9ade64..0029b59f 100644
--- a/apps/update-sources/src/node-modules.ts
+++ b/apps/update-sources/src/node-modules.ts
@@ -44,7 +44,7 @@ const updatePackageJson = async(workspaceDir: string, updates: object) => {
 
 
 const prefetchNpmDeps = (workspaceDir: string): string => {
-    npmRun(['install', '--package-lock-only'], workspaceDir);
+    npmRun(['update', '--package-lock-only'], workspaceDir);
 
     return spawnSync(
         'prefetch-npm-deps',
diff --git a/devShells/default.nix b/devShells/default.nix
index 760e3e0a..be9270c9 100644
--- a/devShells/default.nix
+++ b/devShells/default.nix
@@ -18,8 +18,13 @@
     };
     text = ''
       # this command might fail but still updates the main lockfile
-      npm i --package-lock-only || true
-      prefetch-npm-deps ./package-lock.json
+      npm update --package-lock-only || true
+      hash="$(prefetch-npm-deps ./package-lock.json)"
+      echo "$hash"
+
+      if [[ -f ./default.nix ]]; then
+          sed -i "s#npmDepsHash = .*#npmDepsHash = \"$hash\";#" ./default.nix
+      fi
     '';
   };
 in