diff --git a/scripts/ci/setup-slackware-buildenv.sh b/scripts/ci/setup-slackware-buildenv.sh
index e989c83..031cbc0 100755
--- a/scripts/ci/setup-slackware-buildenv.sh
+++ b/scripts/ci/setup-slackware-buildenv.sh
@@ -75,7 +75,8 @@ if command -v slackpkg > /dev/null 2>&1; then
   slackpkg -batch=on -default_answer=y update
   slackpkg -batch=on -default_answer=y install \
     gcc gcc-g++ binutils make m4 perl autoconf automake libtool pkg-config \
-    curl nghttp2 brotli cyrus-sasl ca-certificates glib2 libcap fuse3
+    curl nghttp2 brotli cyrus-sasl ca-certificates glib2 libcap fuse3 \
+    cmake libarchive lz4 libxml2 guile gc kernel-headers flex elfutils
 else
   echo "==> slackpkg not found, assuming toolchain is already provided by the base image"
 fi
@@ -134,7 +135,9 @@ if ! pkg-config --exists yajl 2>/dev/null; then
     exit 1
   }
   mkdir -p "$d/src" && tar -xf "$d/src.tar.gz" -C "$d/src" --strip-components=1
-  # yajl uses its own cmake-free ./configure wrapper script.
+  # yajl's ./configure is a thin wrapper around CMake (not a cmake-free
+  # autoconf script, despite its name) — cmake must already be on PATH,
+  # see the slackpkg install list in step 0 above.
   ( cd "$d/src" && ./configure -p /usr && make -C build install )
   ldconfig 2>/dev/null || true
 else