1 files changed, 3 insertions, 0 deletions
diff --git a/Lib/pkgutil.py b/Lib/pkgutil.py
index e37ad451966..9180eaed84d 100644
--- a/Lib/pkgutil.py
+++ b/Lib/pkgutil.py
@@ -119,6 +119,9 @@ def iter_modules(path=None, prefix=''):
     """
     if path is None:
         importers = iter_importers()
+    elif isinstance(path, str):
+        raise ValueError("path must be None or list of paths to look for "
+                        "modules in")
     else:
         importers = map(get_importer, path)