diff --git a/stepmania/src/arch/Threads/Threads_Pthreads.cpp b/stepmania/src/arch/Threads/Threads_Pthreads.cpp
index 9f25e656ce..dec054038c 100644
--- a/stepmania/src/arch/Threads/Threads_Pthreads.cpp
+++ b/stepmania/src/arch/Threads/Threads_Pthreads.cpp
@@ -109,7 +109,7 @@ MutexImpl_Pthreads::~MutexImpl_Pthreads()
 }
 
 
-#if defined(HAVE_PTHREAD_MUTEX_TIMEDLOCK)
+#if defined(HAVE_PTHREAD_MUTEX_TIMEDLOCK) || defined(HAVE_PTHREAD_COND_TIMEDWAIT)
 static bool UseTimedlock()
 {
 #if defined(LINUX)
@@ -261,6 +261,7 @@ EventImpl *MakeEvent( MutexImpl *pMutex )
 	return new EventImpl_Pthreads( pPthreadsMutex );
 }
 
+#if 0
 SemaImpl_Pthreads::SemaImpl_Pthreads( int iInitialValue )
 {
 	sem_init( &sem, 0, iInitialValue );
@@ -306,6 +307,113 @@ bool SemaImpl_Pthreads::TryWait()
 		RageException::Throw( "TryWait: sem_trywait failed: %s", strerror(errno) );
 	return true;
 }
+#else
+/* Use conditions, to work around OSX "forgetting" to implement semaphores. */
+SemaImpl_Pthreads::SemaImpl_Pthreads( int iInitialValue )
+{
+	int ret = pthread_cond_init( &m_Cond, NULL );
+	ASSERT_M( ret == 0, ssprintf( "SemaImpl_Pthreads: pthread_cond_init: %s", strerror(errno)) );
+	ret = pthread_mutex_init( &m_Mutex, NULL );
+	ASSERT_M( ret == 0, ssprintf( "SemaImpl_Pthreads: pthread_mutex_init: %s", strerror(errno)) );
+		
+	m_iValue = iInitialValue;
+}
+
+SemaImpl_Pthreads::~SemaImpl_Pthreads()
+{
+	pthread_cond_destroy( &m_Cond );
+	pthread_mutex_destroy( &m_Mutex );
+}
+
+void SemaImpl_Pthreads::Post()
+{
+	pthread_mutex_lock( &m_Mutex );
+	++m_iValue;
+	if( m_iValue == 1 )
+		pthread_cond_signal( &m_Cond );
+	pthread_mutex_unlock( &m_Mutex );
+}
+
+bool SemaImpl_Pthreads::Wait()
+{
+#if defined(HAVE_PTHREAD_COND_TIMEDWAIT)
+	if( UseTimedlock() )
+	{
+		timeval tv;
+		gettimeofday( &tv, NULL );
+
+		/* Wait for ten seconds.  If it takes longer than that, we're probably deadlocked. */
+		timespec ts;
+		ts.tv_sec = tv.tv_sec + 10;
+		ts.tv_nsec = tv.tv_usec * 1000;
+
+		pthread_mutex_lock( &m_Mutex );
+
+		int tries = 2;
+		while( !m_iValue && tries )
+		{
+			int ret = pthread_cond_timedwait( &m_Cond, &m_Mutex, &ts );
+
+			switch( ret )
+			{
+			case 0:
+			case EINTR:
+				break;
+
+			case ETIMEDOUT:
+				/* Timed out.  Probably deadlocked.  Try again one more time, with a smaller
+				 * timeout, just in case we're debugging and happened to stop while waiting
+				 * on the mutex. */
+				++ts.tv_sec;
+				tries--;
+				break;
+
+			default:
+				FAIL_M( ssprintf("pthread_mutex_timedlock: %s", strerror(errno)) );
+			}
+		}
+
+		if( !m_iValue )
+		{
+			/* Timed out. */
+			pthread_mutex_unlock( &m_Mutex );
+			return false;
+		}
+		else
+		{
+			--m_iValue;
+			pthread_mutex_unlock( &m_Mutex );
+			return true;
+		}
+	}
+#endif
+
+	pthread_mutex_lock( &m_Mutex );
+	while( !m_iValue )
+		pthread_cond_wait( &m_Cond, &m_Mutex );
+
+	--m_iValue;
+	pthread_mutex_unlock( &m_Mutex);
+
+	return true;
+}
+
+bool SemaImpl_Pthreads::TryWait()
+{
+	pthread_mutex_lock( &m_Mutex );
+	if( !m_iValue )
+	{
+		pthread_mutex_unlock( &m_Mutex);
+		return false;
+	}
+	
+	--m_iValue;
+	pthread_mutex_unlock( &m_Mutex);
+
+	return true;
+}
+
+#endif
 
 SemaImpl *MakeSemaphore( int iInitialValue )
 {
diff --git a/stepmania/src/arch/Threads/Threads_Pthreads.h b/stepmania/src/arch/Threads/Threads_Pthreads.h
index 2a6dd7596d..ee1415f4af 100644
--- a/stepmania/src/arch/Threads/Threads_Pthreads.h
+++ b/stepmania/src/arch/Threads/Threads_Pthreads.h
@@ -61,6 +61,7 @@ private:
 	pthread_cond_t m_Cond;
 };
 
+#if 0
 class SemaImpl_Pthreads: public SemaImpl
 {
 public:
@@ -74,6 +75,24 @@ public:
 private:
 	sem_t sem;
 };
+#else
+class SemaImpl_Pthreads: public SemaImpl
+{
+public:
+	SemaImpl_Pthreads( int iInitialValue );
+	~SemaImpl_Pthreads();
+	int GetValue() const { return m_iValue; }
+	void Post();
+	bool Wait();
+	bool TryWait();
+
+private:
+	pthread_cond_t m_Cond;
+	pthread_mutex_t m_Mutex;
+	unsigned m_iValue;
+};
+
+#endif
 
 #endif