diff --git a/motmetrics/utils.py b/motmetrics/utils.py
index 74ff37d..51ea633 100644
--- a/motmetrics/utils.py
+++ b/motmetrics/utils.py
@@ -139,6 +139,7 @@ def compute_seuc(a, b, *args, **kwargs):
         oids = np.empty(0)
         hids = np.empty(0)
         weighted_dists = np.empty((0, 0))
+        dists = np.empty((0, 0))
         if fid in fid_to_fgt:
             fgt = fid_to_fgt[fid]
             oids = fgt.index.get_level_values("Id")