diff --git a/test/run-tests.c b/test/run-tests.c
index 17fb0e0c..948d6307 100644
--- a/test/run-tests.c
+++ b/test/run-tests.c
@@ -76,6 +76,16 @@ int main(int argc, char **argv) {
   platform_init(argc, argv);
   argv = uv_setup_args(argc, argv);
 
+  if ((argc == 2 || argc == 4) && strcmp(argv[1], "spawn_helper5") == 0) {
+    uv__check_nfd(4);
+  } else if ((argc == 2 || argc == 4) && strcmp(argv[1], "spawn_tcp_server_helper") == 0) {
+    uv__check_nfd(4);
+  } else if ((argc == 2 || argc == 4) && strcmp(argv[1], "spawn_helper8") == 0) {
+    /* skip */
+  } else {
+    uv__check_nfd(3);
+  }
+
   switch (argc) {
   case 1: return run_tests(0);
   case 2: return maybe_run_test(argc, argv);
diff --git a/test/runner-unix.c b/test/runner-unix.c
index 81560add..e1802dbd 100644
--- a/test/runner-unix.c
+++ b/test/runner-unix.c
@@ -21,6 +21,7 @@
 
 #include "runner-unix.h"
 #include "runner.h"
+#include "task.h"
 
 #include <limits.h>
 #include <stdint.h> /* uintptr_t */
@@ -35,6 +36,7 @@
 #include <sys/wait.h>
 #include <sys/stat.h>
 #include <assert.h>
+#include <fcntl.h>
 
 #include <sys/select.h>
 #include <sys/time.h>
@@ -55,6 +57,67 @@ static void closefd(int fd) {
 }
 
 
+static int uv__cloexec(int fd, int set) {
+  int flags;
+  int r;
+
+  do
+    r = fcntl(fd, F_GETFD);
+  while (r == -1 && errno == EINTR);
+
+  if (r == -1)
+    return errno;
+
+  /* Bail out now if already set/clear. */
+  if (!!(r & FD_CLOEXEC) == !!set)
+    return 0;
+
+  if (set)
+    flags = r | FD_CLOEXEC;
+  else
+    flags = r & ~FD_CLOEXEC;
+
+  do
+    r = fcntl(fd, F_SETFD, flags);
+  while (r == -1 && errno == EINTR);
+
+  if (r)
+    return errno;
+
+  return 0;
+}
+
+
+void uv__check_nfd(int nfd) {
+  const char *arg;
+  int fd;
+  int test_runner_fd = -1;
+  int mode;
+
+  arg = getenv("UV_TEST_RUNNER_FD");
+  if (arg) {
+    test_runner_fd = atoi(arg);
+    ASSERT_GE(test_runner_fd, nfd);
+  }
+
+  for (fd = 0; fd < 2048; fd++) {
+    do
+      mode = fcntl(fd, F_GETFL);
+    while (mode == -1 && errno == EINTR);
+
+    if (fd < nfd || fd == test_runner_fd) {
+      ASSERT_GE(mode, 0);
+    } else if (mode != -1 || errno != EBADF) {
+      /* Try to print some helpful debugging output before the abort. */
+      char args[32];
+      snprintf(args, sizeof(args), "lsof -p %u,%u", getpid(), getppid());
+      system(args);
+      ASSERT_EQ(fd, -1);
+    }
+  }
+}
+
+
 void notify_parent_process(void) {
   char* arg;
   int fd;
@@ -113,11 +176,12 @@ int process_start(char* name, char* part, process_info_t* p, int is_helper) {
   args[n++] = NULL;
 
   stdout_file = tmpfile();
-  stdout_fd = fileno(stdout_file);
   if (!stdout_file) {
     perror("tmpfile");
     return -1;
   }
+  stdout_fd = fileno(stdout_file);
+  uv__cloexec(stdout_fd, 1);
 
   if (is_helper) {
     if (pipe(pipefd)) {
diff --git a/test/task.h b/test/task.h
index e25a9c9a..83a77e05 100644
--- a/test/task.h
+++ b/test/task.h
@@ -326,10 +326,13 @@ extern int snprintf(char*, size_t, const char*, ...);
 
 #if defined(_WIN32)
 #define notify_parent_process() ((void) 0)
+#define uv__check_nfd(nfd) ((void) nfd)
 #else
 extern void notify_parent_process(void);
+extern void uv__check_nfd(int nfd);
 #endif
 
+
 /* Fully close a loop */
 static void close_walk_cb(uv_handle_t* handle, void* arg) {
   if (!uv_is_closing(handle))