diff --git a/class/core/mw.py b/class/core/mw.py
index 1711b0d22..5e87be762 100755
--- a/class/core/mw.py
+++ b/class/core/mw.py
@@ -609,7 +609,7 @@ def getNumLines(path, num, p=1):
                 break
         fp.close()
     except Exception as e:
-        return ''
+        return str(e)
 
     return "\n".join(data)