diff --git a/Dockerfile b/Dockerfile
index ef41ce8..c8dc72d 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -136,10 +136,26 @@ RUN mkdir /etc/sysusers.d \
 # ca-certificates, nix-bin and runit, from Ubuntu's archive. apt fetches
 # them over plain HTTP and checks each one against the archive's signed
 # package lists, so no CA certificates are needed.
-RUN apt-get update \
+#
+# The image's dpkg config drops man pages as each package unpacks, so
+# xz-utils' install, which nix-bin depends on, prints an update-alternatives
+# warning for every man-page link it cannot make. This side file re-includes
+# them for this install alone; it is read after /etc/dpkg/dpkg.cfg.d/excludes,
+# so it overrides the drop and the links are made quietly. The cleanup below
+# removes the man pages and the links and directories they added, then puts
+# the base image's empty man directories back. The image holds exactly what
+# it held before, and installs built from it still drop man pages.
+RUN find /usr/share/man -mindepth 1 -type d > /tmp/base-man-dirs \
+    && echo 'path-include=/usr/share/man/*' > /etc/dpkg/dpkg.cfg.d/z-man \
+    && apt-get update \
     && DEBIAN_FRONTEND=noninteractive apt-get install --yes --no-install-recommends \
         ca-certificates nix-bin runit \
-    && rm -rf /var/lib/apt/lists/*
+    && rm -rf /var/lib/apt/lists/* /etc/dpkg/dpkg.cfg.d/z-man \
+    && find /usr/share/man ! -type d -delete \
+    && find /etc/alternatives -type l -xtype l -delete \
+    && find /usr/share/man -mindepth 1 -type d -empty -delete \
+    && xargs -a /tmp/base-man-dirs mkdir -p \
+    && rm /tmp/base-man-dirs
 
 # Nix run by root expects a group of build users, which nix-bin does not
 # create; with the setting empty, root's builds run without them.