diff --git a/c_cpp_dockerfile b/c_cpp_dockerfile
index f1e1b3a..4cd39e5 100644
--- a/c_cpp_dockerfile
+++ b/c_cpp_dockerfile
@@ -1,6 +1,6 @@
 # for c_cpp
 
-FROM ubuntu:18.04
+FROM ubuntu:20.04
 
 LABEL org.opencontainers.image.authors="Normal-OJ Maintainers <admin@noj.tw>"
 
@@ -8,10 +8,10 @@ LABEL org.opencontainers.image.authors="Normal-OJ Maintainers <admin@noj.tw>"
 RUN apt-get update -y
 
 # install seccomp
-RUN apt-get install seccomp -y
+RUN apt-get install libseccomp-dev -y
 
 # install g++
-RUN apt-get install g++ -y
+RUN apt-get install g++ gcc -y
 
 # sandbox user with uid:1450
 RUN useradd sandbox -u 1450
diff --git a/dispatcher/testdata.py b/dispatcher/testdata.py
index de8b876..4b748ac 100644
--- a/dispatcher/testdata.py
+++ b/dispatcher/testdata.py
@@ -98,7 +98,7 @@ def ensure_testdata(problem_id: int):
     client = get_redis_client()
     key = f'problem-{problem_id}-checksum'
     lock_key = f'{key}-lock'
-    with client.lock(lock_key, timeout=15):
+    with client.lock(lock_key, timeout=60):
         curr_checksum = client.get(key)
         if curr_checksum is not None:
             curr_checksum = curr_checksum.decode()