diff --git a/test/unit_tests/conftest.py b/test/unit_tests/conftest.py
index ebca268..aa173cf 100644
--- a/test/unit_tests/conftest.py
+++ b/test/unit_tests/conftest.py
@@ -194,10 +194,10 @@ def pdf_stream(pdf: fpdf.fpdf.FPDF):
     return pdf.output(dest="S").encode("latin1")
 
 
-def add_image_to_last_page(pdf, image_metadata_pair):
+def add_image_to_last_page(pdf: fpdf.fpdf.FPDF, image_metadata_pair):
     image, metadata = image_metadata_pair
     x, y, w, h = itemgetter("x1", "y1", "width", "height")(metadata)
 
     with tempfile.NamedTemporaryFile(suffix=".png") as temp_image:
         image.save(temp_image.name)
-        pdf.image(temp_image.name, x=x, y=y, w=w, h=h)
+        pdf.image(temp_image.name, x=x, y=y, w=w, h=h, type="png")