diff --git a/test/tw-1637.t b/test/tw-1637.t
new file mode 100755
index 000000000..05ab1f413
--- /dev/null
+++ b/test/tw-1637.t
@@ -0,0 +1,7 @@
+#!/usr/bin/env bash
+. bash_tap_tw.sh
+
+# This problems only appears for "modify", not for "add"
+task add a
+task 1 mod proj:mod
+task 1 _project | grep mod