diff --git a/setup.cfg b/setup.cfg
index 7ca9b19b..34569e80 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -51,6 +51,7 @@ install_requires =
     img2pdf>=0.3.0,<0.5  # pure Python
     pdfminer.six!=20200720,>=20191110,<=20201018
     pikepdf>=2.10.0
+    pikepdf<3;implementation_name=="pypy" and python_version=='3.6'
     pluggy>=0.13.0,<2
     reportlab>=3.5.66
     setuptools