diff --git a/mypy/report.py b/mypy/report.py
index 9e1e156236f2..37b7497f1371 100644
--- a/mypy/report.py
+++ b/mypy/report.py
@@ -140,8 +140,12 @@ def should_skip_path(path: str) -> bool:
 
 def iterate_python_lines(path: str) -> Iterator[tuple[int, str]]:
     """Return an iterator over (line number, line text) from a Python file."""
-    with tokenize.open(path) as input_file:
-        yield from enumerate(input_file, 1)
+    try:
+        with tokenize.open(path) as input_file:
+            yield from enumerate(input_file, 1)
+    except IsADirectoryError:
+        # can happen with namespace packages
+        pass
 
 
 class FuncCounterVisitor(TraverserVisitor):