diff --git a/src/ocrmypdf/optimize.py b/src/ocrmypdf/optimize.py
index 55a8841a..0c6d3b77 100644
--- a/src/ocrmypdf/optimize.py
+++ b/src/ocrmypdf/optimize.py
@@ -454,7 +454,7 @@ def _transcode_png(pike: Pdf, filename: Path, xref: Xref) -> bool:
         img2pdf.convert(fspath(filename), outputstream=f)
 
     with Pdf.open(output) as pdf_image:
-        foreign_image = next(pdf_image.pages[0].images.values())
+        foreign_image = next(iter(pdf_image.pages[0].images.values()))
         local_image = pike.copy_foreign(foreign_image)
 
         im_obj = pike.get_object(xref, 0)
diff --git a/tests/test_image_input.py b/tests/test_image_input.py
index 78ad5fd1..bbce6011 100644
--- a/tests/test_image_input.py
+++ b/tests/test_image_input.py
@@ -87,4 +87,4 @@ def test_jpeg_in_jpeg_out(resources, outpdf):
         'tests/plugins/tesseract_noop.py',
     )
     with pikepdf.open(outpdf) as pdf:
-        assert next(pdf.pages[0].images.values()).Filter == pikepdf.Name.DCTDecode
+        assert next(iter(pdf.pages[0].images.values())).Filter == pikepdf.Name.DCTDecode