diff --git a/src/dotenv/main.py b/src/dotenv/main.py
index 7bc54285..ece9e00a 100644
--- a/src/dotenv/main.py
+++ b/src/dotenv/main.py
@@ -299,10 +299,10 @@ def _is_interactive():
         frame = sys._getframe()
         current_file = __file__
 
-        while frame.f_code.co_filename == current_file or not os.path.exists(
-            frame.f_code.co_filename
+        while frame.f_back is not None and (
+            frame.f_code.co_filename == current_file
+            or not os.path.exists(frame.f_code.co_filename)
         ):
-            assert frame.f_back is not None
             frame = frame.f_back
         frame_filename = frame.f_code.co_filename
         path = os.path.dirname(os.path.abspath(frame_filename))