diff --git a/src/all-nacl.bash b/src/all-nacl.bash
index 817b911c07..0238c2a3e1 100755
--- a/src/all-nacl.bash
+++ b/src/all-nacl.bash
@@ -7,7 +7,7 @@
 
 export GOARCH=386
 export GOOS=nacl
-export GORUN="$GOROOT/misc/nacl/naclrun"
+export GORUN=${GORUN:-$GOROOT/misc/nacl/naclrun}
 
 set -e
 bash make.bash