diff --git a/test.sh b/test.sh
index 271f1fc..84b913f 100755
--- a/test.sh
+++ b/test.sh
@@ -4,13 +4,9 @@ if [ ! -f tools/windowsconstgen.go ]; then
 fi
 set -e
 if [ x$GOOS = xwindows ]; then
-	# have to build windowsconstgen as the host, otherwise weird things happen
-	wcg=`mktemp /tmp/windowsconstgenXXXXXXXXXXXX`
-	GOOS= GOARCH= go build -o $wcg tools/windowsconstgen.go
-	# but we can run it regardless of $GOOS/$GOARCH
-	$wcg . 386 "$@"
-	$wcg . amd64 "$@"
-	rm $wcg
+	# have to invoke go run with the host $GOOS/$GOARCH
+	GOOS= GOARCH= go run tools/windowsconstgen.go . 386 "$@"
+	GOOS= GOARCH= go run tools/windowsconstgen.go . amd64 "$@"
 fi
 cd test
 go build "$@"
diff --git a/tools/windowsconstgen.go b/tools/windowsconstgen.go
index 448b549..0617eb1 100644
--- a/tools/windowsconstgen.go
+++ b/tools/windowsconstgen.go
@@ -182,7 +182,16 @@ func main() {
 	defer f.Close()
 	cmd.Stdout = f
 	cmd.Stderr = os.Stderr
-	cmd.Env = append(cmd.Env, os.Environ()...)		// otherwise $PATH doesn't get carried over and things mysteriously fail
+	// we need to preserve the environment EXCEPT FOR the variables we're overriding
+	// thanks to raggi and smw in irc.freenode.net/#go-nuts
+	for _, ev := range os.Environ() {
+		if strings.HasPrefix(ev, "GOOS=") ||
+			strings.HasPrefix(ev, "GOARCH=") ||
+			strings.HasPrefix(ev, "CGO_ENABLED=") {
+			continue
+		}
+		cmd.Env = append(cmd.Env, ev)
+	}
 	cmd.Env = append(cmd.Env,
 		"GOOS=windows",
 		"GOARCH=" + targetarch,