diff --git a/lib/lyx2lyx/lyxconvert_217.py b/lib/lyx2lyx/lyxconvert_217.py
index 876604ed2c..3b27d54c93 100644
--- a/lib/lyx2lyx/lyxconvert_217.py
+++ b/lib/lyx2lyx/lyxconvert_217.py
@@ -41,7 +41,7 @@ def update_tabular(lines):
             break
 
         new_table = table_update(lines[i:j])
-	lines = lines[:i] + new_table + lines[j:]
+	lines[i:j] = new_table
         i = i + len(new_table)
 
 col_re = re.compile(r'<column alignment="(\d)" valignment="(\d)" leftline="(\d)" rightline="(\d)" width="(.*)" special="(.*)">')