diff --git a/weave b/weave
index 592233e6..b9d1fae5 100755
--- a/weave
+++ b/weave
@@ -1435,7 +1435,7 @@ proxy_args() {
     proxy_parse_args "$@"
 
     if [ -z "$PROXY_TLS_ENABLED" -a -z "$PROXY_TLS_DETECTION_DISABLED" ] && command_exists docker_tls_args ; then
-        if ! DOCKER_TLS_ARGS=$(docker_tls_args ${PROCFS:-/proc}) ; then
+        if ! DOCKER_TLS_ARGS=$(docker_tls_args $PROCFS) ; then
             echo "Unable to auto-detect proxy TLS configuration; you must launch the proxy with" >&2
             echo "'weave launch-proxy' and supply '--no-detect-tls' or TLS options." >&2
             exit 1