diff --git a/Dockerfile b/Dockerfile
index 0926771..a1206d2 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -5,6 +5,10 @@ ARG BUILD_BASE_VERSION=0.5-r3
 RUN --mount=type=cache,sharing=locked,target=/var/cache/apk \
     apk add --update build-base=${BUILD_BASE_VERSION}
 
+ARG CAPNPROTO_VERSION=1.2.0-r0
+RUN --mount=type=cache,sharing=locked,target=/var/cache/apk \
+    apk add --update capnproto=${CAPNPROTO_VERSION}
+
 ARG CARGO_VERSION=1.91.1-r1
 RUN --mount=type=cache,sharing=locked,target=/var/cache/apk \
     apk add --update cargo=${CARGO_VERSION}