diff --git a/cellframenet.py b/cellframenet.py
index b228048f35756c8197582e2eb4bfefc3a9e7ded5..43dd01e1c88e35f7d48e84d84a19acb9f2d20579 100644
--- a/cellframenet.py
+++ b/cellframenet.py
@@ -418,7 +418,7 @@ class CellframeNetwork:
         logIt.notice("ptr = {}" .format(ptr))
         aptr, size = ptr
         #iterate over blocks: atom-pointer should not be none, and size shoud be >0
-        while ptr: 
+        while aptr: 
                 
             if size <= 0: 
                 aptr, size = self.main.atomIterGetNext(iterator)