diff --git a/Dockerfile b/Dockerfile
index 97d9a28..c3a5c01 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -22,6 +22,7 @@
 ENV PATH /usr/local/go/bin:$GOPATH/bin:$PATH
 ENV GOROOT_BOOTSTRAP /usr/local/gobootstrap
 ENV GO_BOOTSTRAP_VERSION go1.13.9
+ARG GO_VERSION
 ENV GO_VERSION ${GO_VERSION}
 
 # Fake time
@@ -93,6 +94,8 @@
 COPY --from=nacl /tmp/sel_ldr_x86_64 /usr/local/bin
 COPY --from=temp_pre_go14 /usr/local/go1.14 /usr/local/go1.14
 
+ARG GO_VERSION
+ENV GO_VERSION ${GO_VERSION}
 ENV GOPATH /go
 ENV PATH /usr/local/go/bin:$GOPATH/bin:$PATH
 
diff --git a/Makefile b/Makefile
index bac164f..56ff930 100644
--- a/Makefile
+++ b/Makefile
@@ -12,7 +12,7 @@
 runlocal:
 	docker network create sandnet || true
 	docker kill play_dev || true
-	docker run --name=play_dev --rm --network=sandnet -ti -p 127.0.0.1:8081:8080/tcp golang/playground
+	docker run --name=play_dev --rm --network=sandnet --env SANDBOX_BACKEND_URL="http://sandbox_dev.sandnet/run" -ti -p 127.0.0.1:8081:8080/tcp golang/playground
 
 test_go:
 	# Run fast tests first: (and tests whether, say, things compile)
diff --git a/tests.go b/tests.go
index 0f3cda4..454b02a 100644
--- a/tests.go
+++ b/tests.go
@@ -29,6 +29,7 @@
 
 func (s *server) testNacl() {
 	log.Printf("testing nacl mode")
+	os.Setenv("GO_VERSION", "")
 	s.runTests()
 }