diff --git a/test/syscalls/linux/cgroup.cc b/test/syscalls/linux/cgroup.cc
index a53c9895d..421df540e 100644
--- a/test/syscalls/linux/cgroup.cc
+++ b/test/syscalls/linux/cgroup.cc
@@ -1214,7 +1214,8 @@ TEST(PIDsCgroup, LimitEnforced) {
               IsPosixErrorOkAndHolds(baseline + 1));
 
   // Exit the first thread and try create a thread again, which should succeed.
-  t1.Join();
+  ASSERT_NO_ERRNO(child.PollControlFileForChangeAfter(
+      "pids.current", absl::Seconds(30), [&t1]() { t1.Join(); }));
   ASSERT_THAT(child.ReadIntegerControlFile("pids.current"),
               IsPosixErrorOkAndHolds(baseline));
   NoopThreads t2(1);
diff --git a/test/util/cgroup_util.cc b/test/util/cgroup_util.cc
index 4e687481f..dca02c6ce 100644
--- a/test/util/cgroup_util.cc
+++ b/test/util/cgroup_util.cc
@@ -87,6 +87,12 @@ PosixErrorOr<absl::flat_hash_set<pid_t>> Cgroup::Tasks() const {
 
 PosixError Cgroup::PollControlFileForChange(absl::string_view name,
                                             absl::Duration timeout) const {
+  return PollControlFileForChangeAfter(name, timeout, []() {});
+}
+
+PosixError Cgroup::PollControlFileForChangeAfter(
+    absl::string_view name, absl::Duration timeout,
+    std::function<void()> body) const {
   const absl::Duration poll_interval = absl::Milliseconds(10);
   const absl::Time deadline = absl::Now() + timeout;
   const std::string alias_path = absl::StrFormat("[cg#%d]/%s", id_, name);
@@ -94,6 +100,8 @@ PosixError Cgroup::PollControlFileForChange(absl::string_view name,
   ASSIGN_OR_RETURN_ERRNO(const int64_t initial_value,
                          ReadIntegerControlFile(name));
 
+  body();
+
   while (true) {
     ASSIGN_OR_RETURN_ERRNO(const int64_t current_value,
                            ReadIntegerControlFile(name));
diff --git a/test/util/cgroup_util.h b/test/util/cgroup_util.h
index f45945b3e..a13f1772d 100644
--- a/test/util/cgroup_util.h
+++ b/test/util/cgroup_util.h
@@ -78,6 +78,11 @@ class Cgroup {
   PosixError PollControlFileForChange(absl::string_view name,
                                       absl::Duration timeout) const;
 
+  // Waits for a control file's value to change after calling body.
+  PosixError PollControlFileForChangeAfter(absl::string_view name,
+                                           absl::Duration timeout,
+                                           std::function<void()> body) const;
+
   // Returns the thread ids of the leaders of thread groups managed by this
   // cgroup.
   PosixErrorOr<absl::flat_hash_set<pid_t>> Procs() const;