diff --git a/tests/test_pdf.py b/tests/test_pdf.py
index 18c85c7ce..3bcc360ac 100644
--- a/tests/test_pdf.py
+++ b/tests/test_pdf.py
@@ -562,8 +562,8 @@ def test_document_info():
         b'006600740065007200a00061006c006c>') in pdf
     assert b'/Keywords (html, css, pdf)' in pdf
     assert b'/Subject <feff0042006c0061006820260020>' in pdf
-    assert b'/CreationDate (20110421230000Z)' in pdf
-    assert b"/ModDate (20130721234600+01'00)" in pdf
+    assert b'/CreationDate (D:20110421230000Z)' in pdf
+    assert b"/ModDate (D:20130721234600+01'00)" in pdf
 
 
 @assert_no_logs
diff --git a/weasyprint/pdf/__init__.py b/weasyprint/pdf/__init__.py
index f37cad858..dd344a32a 100644
--- a/weasyprint/pdf/__init__.py
+++ b/weasyprint/pdf/__init__.py
@@ -45,7 +45,7 @@ def _w3c_date_to_pdf(string, attr_name):
             pdf_date += f"{tz_hour:+03d}'{tz_minute:02d}"
         else:
             pdf_date += 'Z'
-    return pdf_date
+    return f'D:{pdf_date}'
 
 
 def _reference_resources(pdf, resources, images, fonts):