diff --git a/builder.Dockerfile b/builder.Dockerfile
index 1419ca3..716cb09 100644
--- a/builder.Dockerfile
+++ b/builder.Dockerfile
@@ -24,6 +24,10 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
         libasound2-dev \
     && rm -rf /var/lib/apt/lists/*
 
+# Our own Go modules (engines/inkwell, engines/gorpg) are served by the forge,
+# not by proxy.golang.org, and are absent from the public checksum database.
+ENV GOPRIVATE=git.teletypegames.org
+
 WORKDIR /workspace
 
 CMD ["/bin/bash"]
diff --git a/example-makefile.make b/example-makefile.make
index 5841caa..06619e0 100644
--- a/example-makefile.make
+++ b/example-makefile.make
@@ -4,6 +4,10 @@
 
 PROJECT = ebitenginedemo
 
+# Our own modules live on the forge, not on proxy.golang.org: fetch them
+# directly and skip the public checksum database.
+export GOPRIVATE = git.teletypegames.org
+
 BIN_DIR     = bin
 DIST_DIR    = dist
 WASM_NAME   = game.wasm