diff --git a/wsgi.py b/wsgi.py
index 5d757ff..634255f 100644
--- a/wsgi.py
+++ b/wsgi.py
@@ -290,9 +290,12 @@ def tables():
             output_str.append(tfoot)
             output_str.append(table[idx:])
 
-    importance_factor = float(request.args.get("importance"))
+
+    importance_factor = request.args.get("importance")
     if not importance_factor:
         importance_factor = 1.0
+    else:
+        importance_factor = float(importance_factor)
 
     output_str = []