diff --git a/osmxml.py b/osmxml.py
index 29ad3d1..54ed260 100644
--- a/osmxml.py
+++ b/osmxml.py
@@ -208,7 +208,7 @@ class mstr_osmxml:
     # Again, a crash on number checking of levels.
     # Short call for sanity check
 
-    def is_float(element: any) -> bool:
+    def is_float(self, element: any) -> bool:
         #If you expect None to be passed:
         if element is None: 
             return False