diff --git a/readTrace.py b/readTrace.py
index c39202f46809f98416b61b07a53171edf7144611..9db686703e3ae6f1f7eb691fce32ccc75d8fb2b2 100755
--- a/readTrace.py
+++ b/readTrace.py
@@ -118,9 +118,9 @@ class Block() :
       stats = self.stats[v]
       versions.append([])
       englobChar = "-"
-      if version[0].actionCost > version[0].oracleCost :
+      if len(version) > 0 and version[0].actionCost > version[0].oracleCost :
         englobChar = "~"
-      lineStr = englobStr(version[0].word, englobChar, lenLine())
+      lineStr = englobStr("" if len(version) == 0 else version[0].word, englobChar, lenLine())
       versions[-1].append(lineStr + (lenLine()-len(lineStr))*" ")
       for step in version :
         versions[-1].append(str(step) + (lenLine()-len(str(step)))*" ")