diff --git a/sys/kern/syscall.c b/sys/kern/syscall.c
index a0b4d21..fb42f96 100644
--- a/sys/kern/syscall.c
+++ b/sys/kern/syscall.c
@@ -440,7 +440,7 @@ Syscall_ThreadSleep(uint64_t time)
 uint64_t
 Syscall_ThreadWait(uint64_t tid)
 {
-    int status;
+    uint64_t status;
     Thread *cur = Sched_Current();
 
     /*
diff --git a/tests/pthreadtest.c b/tests/pthreadtest.c
index 0cdc81c..e931279 100644
--- a/tests/pthreadtest.c
+++ b/tests/pthreadtest.c
@@ -5,8 +5,8 @@
 #include <string.h>
 
 #include <pthread.h>
-#include <stdbool.h>
-#include <core/mutex.h>
+
+pthread_mutex_t mtx;
 
 void *
 thread_simple(void *arg)
@@ -16,9 +16,27 @@ thread_simple(void *arg)
     return arg;
 }
 
+void *
+thread_lock(void *arg)
+{
+    int i;
+    int status;
+
+    for (i = 0; i < 100; i++) {
+	status = pthread_mutex_lock(&mtx);
+	assert(status == 0);
+	pthread_yield();
+	status = pthread_mutex_unlock(&mtx);
+	assert(status == 0);
+    }
+
+    return NULL;
+}
+
 int
 main(int argc, const char *argv[])
 {
+    int i;
     int status;
     pthread_t thr;
     void *result;
@@ -42,6 +60,32 @@ main(int argc, const char *argv[])
     assert(result == (void *)1);
 
     // Mutex test
+    printf("simple mutex lock test\n");
+    status = pthread_mutex_init(&mtx, NULL);
+    assert(status == 0);
+    status = pthread_mutex_lock(&mtx);
+    assert(status == 0);
+    status = pthread_mutex_unlock(&mtx);
+    assert(status == 0);
+    status = pthread_mutex_destroy(&mtx);
+    assert(status == 0);
+
+    // Mutex Contention Test
+    printf("contended mutex lock test\n");
+    pthread_mutex_init(&mtx, NULL);
+    status = pthread_create(&thr, NULL, thread_simple, (void *)1);
+    assert(status == 0);
+    for (i = 0; i < 100; i++) {
+	status = pthread_mutex_lock(&mtx);
+	assert(status == 0);
+	pthread_yield();
+	pthread_mutex_unlock(&mtx);
+	assert(status == 0);
+    }
+    status = pthread_join(thr, &result);
+    assert(status == 0);
+    status = pthread_mutex_destroy(&mtx);
+    assert(status == 0);
 
     printf("Success!\n");