diff --git a/include/errno.h b/include/errno.h
index 4c2d3c3..1c1cbad 100644
--- a/include/errno.h
+++ b/include/errno.h
@@ -2,17 +2,17 @@
 #ifndef __ERRNO_H__
 #define __ERRNO_H__
 
-#define EIO		0xBAD1
-#define EBADF		0xBAD2
-#define EINVAL		0xBAD3
-#define EFAULT		0xBAD4
-#define ENOMEM		0xBAD5
-#define ENOENT		0xBAD6
-#define ENOTDIR		0xBAD7
-#define ENAMETOOLONG	0xBAD8
-#define ENOSYS		0xBAD9
-#define EAGAIN		0xBADA
-#define EBUSY		0xBADB
+#define EIO		0x1BAD0001
+#define EBADF		0x1BAD0002
+#define EINVAL		0x1BAD0003
+#define EFAULT		0x1BAD0004
+#define ENOMEM		0x1BAD0005
+#define ENOENT		0x1BAD0006
+#define ENOTDIR		0x1BAD0007
+#define ENAMETOOLONG	0x1BAD0008
+#define ENOSYS		0x1BAD0009
+#define EAGAIN		0x1BAD000A
+#define EBUSY		0x1BAD000B
 
 #endif /* __ERRNO_H__ */
 
diff --git a/lib/libc/posix/pthread.c b/lib/libc/posix/pthread.c
index cc9199c..d37e768 100644
--- a/lib/libc/posix/pthread.c
+++ b/lib/libc/posix/pthread.c
@@ -90,7 +90,9 @@ pthreadCreateHelper(void *arg)
 {
     struct pthread *thr = (struct pthread *)arg;
 
-    OSThreadExit((uint64_t)(thr->entry)(thr->arg));
+    thr->result = (thr->entry)(thr->arg);
+
+    OSThreadExit(0);
 }
 
 int
@@ -141,8 +143,8 @@ int
 pthread_join(pthread_t thread, void **value_ptr)
 {
     struct pthread *thr = thread;
-    uint64_t status = OSThreadWait(thr->tid);
-    if (status != 0) {
+    uint64_t status = OSThreadWait(0);//thr->tid);
+    if (SYSCALL_ERRCODE(status) != 0) {
 	return status;
     }
 
diff --git a/sys/kern/syscall.c b/sys/kern/syscall.c
index d8fcc71..a0b4d21 100644
--- a/sys/kern/syscall.c
+++ b/sys/kern/syscall.c
@@ -365,13 +365,13 @@ Syscall_ThreadCreate(uint64_t rip, uint64_t arg)
 
     Thread_Release(curThread);
     if (newThread == NULL) {
-	return -1;
+	return SYSCALL_PACK(ENOMEM, 0);
     }
 
     threadId = newThread->tid;
     Sched_SetRunnable(newThread);
 
-    return threadId;
+    return SYSCALL_PACK(0, threadId);
 }
 
 uint64_t
@@ -455,7 +455,7 @@ Syscall_ThreadWait(uint64_t tid)
     while (1) {
 	Semaphore_Acquire(&cur->proc->zombieSemaphore);
 	status = Thread_Wait(cur, tid);
-	if (status != 0) {
+	if (SYSCALL_ERRCODE(status) != EAGAIN) {
 	    Thread_Release(cur);
 	    return status;
 	}
diff --git a/sys/kern/thread.c b/sys/kern/thread.c
index b1a665c..23f7e7c 100644
--- a/sys/kern/thread.c
+++ b/sys/kern/thread.c
@@ -3,6 +3,9 @@
 #include <stdint.h>
 #include <string.h>
 
+#include <errno.h>
+#include <sys/syscall.h>
+
 #include <sys/kassert.h>
 #include <sys/kconfig.h>
 #include <sys/kdebug.h>
@@ -382,13 +385,13 @@ Thread_Wait(Thread *thr, uint64_t tid)
     if (tid == 0) {
 	t = TAILQ_FIRST(&thr->proc->zombieQueue);
 	if (!t) {
-	    return 0;
+	    return SYSCALL_PACK(EAGAIN, 0);
 	}
 
 	TAILQ_REMOVE(&thr->proc->zombieQueue, t, schedQueue);
 	status = t->exitValue;
 	Thread_Release(t);
-	return status;
+	return SYSCALL_PACK(0, status);
     }
 
     TAILQ_FOREACH(t, &thr->proc->zombieQueue, schedQueue) {
@@ -396,7 +399,7 @@ Thread_Wait(Thread *thr, uint64_t tid)
 	    TAILQ_REMOVE(&thr->proc->zombieQueue, t, schedQueue);
 	    status = t->exitValue;
 	    Thread_Release(t);
-	    return status;
+	    return SYSCALL_PACK(0, status);
 	}
     }
 
diff --git a/tests/pthreadtest.c b/tests/pthreadtest.c
index fbca42c..0cdc81c 100644
--- a/tests/pthreadtest.c
+++ b/tests/pthreadtest.c
@@ -5,6 +5,8 @@
 #include <string.h>
 
 #include <pthread.h>
+#include <stdbool.h>
+#include <core/mutex.h>
 
 void *
 thread_simple(void *arg)
@@ -26,10 +28,8 @@ main(int argc, const char *argv[])
     // Simple thread test
     printf("simple test\n");
     status = pthread_create(&thr, NULL, thread_simple, NULL);
-    printf("status %d\n", status);
     assert(status == 0);
     status = pthread_join(thr, &result);
-    printf("status %d\n", status);
     assert(status == 0);
     assert(result == NULL);
 
@@ -41,6 +41,8 @@ main(int argc, const char *argv[])
     assert(status == 0);
     assert(result == (void *)1);
 
+    // Mutex test
+
     printf("Success!\n");
 
     return 0;