Unable to spawn isolate after updating Dart SDK

[Bikeman868]

I checked that pub build worked without errors before updating the Dart SDK. Immediately after updating pub build fails with this error

Loading source assets...
Loading dart_to_js_script_rewriter transformers...
Unable to spawn isolate: Unhandled exception:
Could not import "package:$pub/transformer_isolate.dart" from "file:///C:/Users/Martin/AppData/Local/Temp/pub_8fefe270-7420-11e7-82f4-600292272768/runInIsolate.dart": Failure getting http://localhost:53638/packages/$pub/transformer_isolate.dart:  404 Not Found
null

I updated from SDK 1.11.3 to 1.24.2. After getting this error I tried pub get just in case but this didn't help.

[Bikeman868]

This turned out to be an incomplete install of the SDK which had missing files.