diff --git a/conf/nextpnr/requirements.txt b/conf/nextpnr/requirements.txt
index 2b8ac54b..3876edd8 100644
--- a/conf/nextpnr/requirements.txt
+++ b/conf/nextpnr/requirements.txt
@@ -1,4 +1,5 @@
 # Can be removed after merging https://github.com/SymbiFlow/prjxray/pull/1550
+pycapnp==1.1.0
 pyyaml
 fasm
 git+https://github.com/SymbiFlow/prjxray.git#egg=prjxray