diff --git a/docker/test/fasttest/Dockerfile b/docker/test/fasttest/Dockerfile
index 2512268be0f..4cac2ee6135 100644
--- a/docker/test/fasttest/Dockerfile
+++ b/docker/test/fasttest/Dockerfile
@@ -26,7 +26,10 @@ RUN apt-get update \
         zstd \
         --yes --no-install-recommends \
     && apt-get clean \
-    && rm -rf /var/lib/apt/lists/* /var/cache/debconf /tmp/*
+    && rm -rf /var/lib/apt/lists/* /var/cache/debconf /tmp/* \
+    && groupadd --system --gid 1000 clickhouse \
+    && useradd --system --gid 1000 --uid 1000 -m clickhouse
+# ^ For some reason, groupadd and useradd are needed for tests with 'expect', but I don't know, why.
 
 COPY requirements.txt /
 RUN pip3 install --no-cache-dir -r /requirements.txt
diff --git a/docker/test/fasttest/run.sh b/docker/test/fasttest/run.sh
index 0d975d64010..970bf12a81a 100755
--- a/docker/test/fasttest/run.sh
+++ b/docker/test/fasttest/run.sh
@@ -9,7 +9,7 @@ trap 'kill $(jobs -pr) ||:' EXIT
 stage=${stage:-}
 
 # Compiler version, normally set by Dockerfile
-export LLVM_VERSION=${LLVM_VERSION:-17}
+export LLVM_VERSION=${LLVM_VERSION:-18}
 
 # A variable to pass additional flags to CMake.
 # Here we explicitly default it to nothing so that bash doesn't complain about
diff --git a/docker/test/util/Dockerfile b/docker/test/util/Dockerfile
index f13bb576f79..babddbd228c 100644
--- a/docker/test/util/Dockerfile
+++ b/docker/test/util/Dockerfile
@@ -17,6 +17,7 @@ ENV DEBIAN_FRONTEND=noninteractive LLVM_VERSION=18
 
 RUN apt-get update \
     && apt-get install \
+        sudo \
         apt-transport-https \
         apt-utils \
         ca-certificates \