diff --git a/test/runner-unix.c b/test/runner-unix.c
index c7cf9a139..1a54a1adb 100644
--- a/test/runner-unix.c
+++ b/test/runner-unix.c
@@ -55,8 +55,13 @@ void platform_init(int argc, char **argv) {
 
 /* Invoke "argv[0] test-name [test-part]". Store process info in *p. */
 /* Make sure that all stdio output of the processes is buffered up. */
-int process_start(char* name, char* part, process_info_t* p) {
-  FILE* stdout_file = tmpfile();
+int process_start(char* name, char* part, process_info_t* p, int is_helper) {
+  FILE* stdout_file;
+  const char* arg;
+  char* args[16];
+  int n;
+
+  stdout_file = tmpfile();
   if (!stdout_file) {
     perror("tmpfile");
     return -1;
@@ -74,11 +79,28 @@ int process_start(char* name, char* part, process_info_t* p) {
 
   if (pid == 0) {
     /* child */
+    arg = getenv("UV_USE_VALGRIND");
+    n = 0;
+
+    /* Disable valgrind for helpers, it complains about helpers leaking memory.
+     * They're killed after the test and as such never get a chance to clean up.
+     */
+    if (is_helper == 0 && arg != NULL && atoi(arg) != 0) {
+      args[n++] = "valgrind";
+      args[n++] = "--quiet";
+      args[n++] = "--leak-check=full";
+      args[n++] = "--show-reachable=yes";
+      args[n++] = "--error-exitcode=125";
+    }
+
+    args[n++] = executable_path;
+    args[n++] = name;
+    args[n++] = part;
+    args[n++] = NULL;
+
     dup2(fileno(stdout_file), STDOUT_FILENO);
     dup2(fileno(stdout_file), STDERR_FILENO);
-
-    char* args[] = { executable_path, name, part, NULL };
-    execvp(executable_path, args);
+    execvp(args[0], args);
     perror("execvp()");
     _exit(127);
   }
diff --git a/test/runner-win.c b/test/runner-win.c
index 2f44ff33a..c304a04a1 100644
--- a/test/runner-win.c
+++ b/test/runner-win.c
@@ -57,7 +57,7 @@ void platform_init(int argc, char **argv) {
 }
 
 
-int process_start(char *name, char *part, process_info_t *p) {
+int process_start(char *name, char *part, process_info_t *p, int is_helper) {
   HANDLE file = INVALID_HANDLE_VALUE;
   HANDLE nul = INVALID_HANDLE_VALUE;
   WCHAR path[MAX_PATH], filename[MAX_PATH];
diff --git a/test/runner.c b/test/runner.c
index b34acc843..55d2a37ed 100644
--- a/test/runner.c
+++ b/test/runner.c
@@ -147,7 +147,8 @@ int run_test(const char* test, int timeout, int benchmark_output) {
 
     if (process_start(task->task_name,
                       task->process_name,
-                      &processes[process_count]) == -1) {
+                      &processes[process_count],
+                      1 /* is_helper */) == -1) {
       snprintf(errmsg,
                sizeof errmsg,
                "Process `%s` failed to start.",
@@ -173,7 +174,8 @@ int run_test(const char* test, int timeout, int benchmark_output) {
 
     if (process_start(task->task_name,
                       task->process_name,
-                      &processes[process_count]) == -1) {
+                      &processes[process_count],
+                      0 /* !is_helper */) == -1) {
       snprintf(errmsg,
                sizeof errmsg,
                "Process `%s` failed to start.",
diff --git a/test/runner.h b/test/runner.h
index 5cee695ed..0358d7e25 100644
--- a/test/runner.h
+++ b/test/runner.h
@@ -127,7 +127,7 @@ void platform_init();
 
 /* Invoke "argv[0] test-name [test-part]". Store process info in *p. */
 /* Make sure that all stdio output of the processes is buffered up. */
-int process_start(char *name, char* part, process_info_t *p);
+int process_start(char *name, char* part, process_info_t *p, int is_helper);
 
 /* Wait for all `n` processes in `vec` to terminate. */
 /* Time out after `timeout` msec, or never if timeout == -1 */