diff --git a/IPython/core/oinspect.py b/IPython/core/oinspect.py
index 67eb771..4348746 100644
--- a/IPython/core/oinspect.py
+++ b/IPython/core/oinspect.py
@@ -326,6 +326,8 @@ def find_source_lines(obj):
             # For instances, try the class object like getsource() does
             if hasattr(obj, '__class__'):
                 lineno = inspect.getsourcelines(obj.__class__)[1]
+            else:
+                lineno = None
     except:
         return None