diff --git a/layers/box_utils.py b/layers/box_utils.py
index 41b244273..46a83351e 100644
--- a/layers/box_utils.py
+++ b/layers/box_utils.py
@@ -130,7 +130,7 @@ def encode(matched, priors, variances):
     g_cxcy /= (variances[0] * priors[:, 2:])
     # match wh / prior wh
     g_wh = (matched[:, 2:] - matched[:, :2]) / priors[:, 2:]
-    g_wh = torch.log(g_wh) / variances[1]
+    g_wh = torch.log(g_wh + 1e-10) / variances[1]
     # return target for smooth_l1_loss
     return torch.cat([g_cxcy, g_wh], 1)  # [num_priors,4]