diff --git a/artiq/tools.py b/artiq/tools.py
index 9e443fb6b..dfd9ef0bb 100644
--- a/artiq/tools.py
+++ b/artiq/tools.py
@@ -57,6 +57,8 @@ def short_format(v):
         r = t.__name__
         if t is list or t is dict or t is set:
             r += " ({})".format(len(v))
+        if t is np.ndarray:
+            r += " " + str(np.shape(v))
         return r