Build failes SCSS undefined variable

When I try to build a newly created project, I get the following error message:

[INF] -compile-sass:

[INF] writing sass content to D:\ISMed\Source\Sencha\workspace-ext-4.2.1/build/temp/production/MyApp/sass/MyApp-all.scss

[INF] appending sass content to D:\ISMed\Source\Sencha\workspace-ext-4.2.1/build/temp/production/MyApp/sass/MyApp-all.scss

[INF] appending sass content to D:\ISMed\Source\Sencha\workspace-ext-4.2.1/build/temp/production/MyApp/sass/MyApp-all.scss

[INF] executing compass using system installed ruby runtime

error MyApp-all.scss (Line 1 of ../../../../../ext/packages/ext-theme-neptune/sass/var/window/Window.scss: Undefined variable: "$base-highlight-color".)

overwrite MyApp-all.css

[ERR]

[ERR] BUILD FAILED

[ERR] com.sencha.exceptions.ExProcess: compass process exited with non-zero code : 1

I use:

Version: 3.0.4.1386

Channel: 3.0.1-stable

Platform: 1.3.0.803

Cmd: 4.0.2.67

Framework: ExtJS 4.2.x

Thanks