diff --git a/tests/run-tests b/tests/run-tests
index dce080a8..935ceb8e 100755
--- a/tests/run-tests
+++ b/tests/run-tests
@@ -1266,7 +1266,7 @@ if which wget; then
     mv $REPOROOT/index-v1.json repo/index-v1.json
 
     port=321${RANDOM:3}
-    test $(printf $port | wc --chars) -le 3 && port=52734 # when $RANDOM doesn't work
+    test $(printf $port | wc -m) -le 3 && port=52734 # when $RANDOM doesn't work
     timeout 5m python3 -m http.server $port --bind 127.0.0.1 > $REPOROOT/http.server.log 2>&1 &
     http_server_pid=$!