diff --git a/actions/ost-compare-structures b/actions/ost-compare-structures
index fbae451dcb0dcaf34f906674b84d22c3063ad67a..cfaabbd373dd53b9b53c6282ae21148a59b46c25 100644
--- a/actions/ost-compare-structures
+++ b/actions/ost-compare-structures
@@ -81,6 +81,7 @@ import json
 import time
 import sys
 import traceback
+import math
 
 from ost import io
 from ost.mol.alg import scoring
@@ -497,7 +498,7 @@ def _ParseArgs():
 def _RoundOrNone(num, decimals = 3):
     """ Helper to create valid JSON output
     """
-    if num is None:
+    if num is None or math.isnan(num) or math.isinf(num):
         return None
     return round(num, decimals)