diff --git a/docker-contributor/Dockerfile b/docker-contributor/Dockerfile
index 85780c97..05fcbdac 100644
--- a/docker-contributor/Dockerfile
+++ b/docker-contributor/Dockerfile
@@ -24,7 +24,7 @@ RUN apt update \
     nginx php8.1 php8.1-cli php8.1-fpm php8.1-zip \
     php8.1-gd php8.1-curl php8.1-mysql php8.1-intl \
     php8.1-gmp php8.1-xml php8.1-mbstring php8.1-xdebug php8.1-pcov \
-    bsdmainutils ntp \
+    bsdmainutils ntp lsof \
     linuxdoc-tools linuxdoc-tools-text groff \
     python3-sphinx python3-sphinx-rtd-theme python3-pip fontconfig python3-yaml \
     texlive-latex-recommended texlive-latex-extra \
diff --git a/docker/judgehost/Dockerfile b/docker/judgehost/Dockerfile
index 94b0a00d..0f06dcd9 100644
--- a/docker/judgehost/Dockerfile
+++ b/docker/judgehost/Dockerfile
@@ -14,7 +14,7 @@ ENV DEBIAN_FRONTEND=noninteractive \
 RUN apt update \
 	&& apt install --no-install-recommends --no-install-suggests -y \
 	dumb-init \
-	acl zip unzip supervisor sudo procps libcgroup2 \
+	acl lsof zip unzip supervisor sudo procps libcgroup2 \
 	php-cli php-zip php-gd php-curl php-mysql php-json \
 	php-gmp php-xml php-mbstring python3 \
 	gcc g++ default-jre-headless default-jdk ghc fp-compiler \