diff --git a/cmd/gui/docker/win-builder/Dockerfile b/cmd/gui/docker/win-builder/Dockerfile
index cdd4290..570749c 100644
--- a/cmd/gui/docker/win-builder/Dockerfile
+++ b/cmd/gui/docker/win-builder/Dockerfile
@@ -36,9 +36,11 @@ RUN dpkg --add-architecture i386 \
 
 # electron-builder resolves the uninstaller via the system wine when
 # USE_SYSTEM_WINE=true (or by default on Linux without a toolset). Pin it.
+# The toolchain cache lives in $HOME/.cache (mounted as a volume by
+# dist-win-docker.sh), so it is reused across builds and never pollutes the
+# mounted workspace.
 ENV USE_SYSTEM_WINE=true
 ENV WINEDEBUG=-all
-ENV ELECTRON_BUILDER_CACHE=/workspace/cmd/gui/.cache
 
 # LuaJIT cross-compiled for Windows; keeps lua51.dll and the cgo import lib
 # (libluajit-5.1.dll.a -> libluajit-5.1.a in the mingw lib dir).