diff --git a/doc/build-unix.md b/doc/build-unix.md
index 04f757ba52..bfb3bd35d9 100644
--- a/doc/build-unix.md
+++ b/doc/build-unix.md
@@ -163,6 +163,12 @@ SQLite is required for the wallet:
 
 To build Bitcoin Core without the wallet, see [*Disable-wallet mode*](#disable-wallet-mode)
 
+Cap'n Proto is needed for IPC functionality (see [multiprocess.md](multiprocess.md)):
+
+    apk add capnproto capnproto-dev
+
+Compile with `-DENABLE_IPC=OFF` if you do not need IPC functionality.
+
 ZMQ dependencies (provides ZMQ API):
 
     apk add zeromq-dev
@@ -205,7 +211,7 @@ Setup and Build Example: Arch Linux
 -----------------------------------
 This example lists the steps necessary to setup and build a command line only distribution of the latest changes on Arch Linux:
 
-    pacman --sync --needed cmake boost gcc git libevent make python sqlite
+    pacman --sync --needed capnproto cmake boost gcc git libevent make python sqlite
     git clone https://github.com/bitcoin/bitcoin.git
     cd bitcoin/
     cmake -B build