diff --git a/stepmania/src/arch/Threads/Threads_Pthreads.cpp b/stepmania/src/arch/Threads/Threads_Pthreads.cpp
index 5f08f5bfa5..f6a8f0ee2e 100644
--- a/stepmania/src/arch/Threads/Threads_Pthreads.cpp
+++ b/stepmania/src/arch/Threads/Threads_Pthreads.cpp
@@ -222,6 +222,7 @@ MutexImpl *MakeMutex( RageMutex *pParent )
 	return new MutexImpl_Pthreads( pParent );
 }
 
+#if 0
 SemaImpl_Pthreads::SemaImpl_Pthreads( int iInitialValue )
 {
 	sem_init( &sem, 0, iInitialValue );
@@ -267,6 +268,61 @@ 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()
+{
+	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 299f9aaf61..d17716abd7 100644
--- a/stepmania/src/arch/Threads/Threads_Pthreads.h
+++ b/stepmania/src/arch/Threads/Threads_Pthreads.h
@@ -53,6 +53,7 @@ private:
 	pthread_mutex_t mutex;
 };
 
+#if 0
 class SemaImpl_Pthreads: public SemaImpl
 {
 public:
@@ -66,6 +67,24 @@ 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