diff --git a/include/bx/macros.h b/include/bx/macros.h
index 8e7b45f..3a82d7d 100644
--- a/include/bx/macros.h
+++ b/include/bx/macros.h
@@ -107,7 +107,7 @@
 #endif // BX_CONFIG_CRT_FILE_READER_WRITER
 
 #ifndef BX_CONFIG_SEMAPHORE_PTHREAD
-#	define BX_CONFIG_SEMAPHORE_PTHREAD 0
+#	define BX_CONFIG_SEMAPHORE_PTHREAD BX_PLATFORM_OSX|BX_PLATFORM_IOS
 #endif // BX_CONFIG_SEMAPHORE_PTHREAD
 
 #endif // __BX_MACROS_H__
diff --git a/include/bx/sem.h b/include/bx/sem.h
index e7f1db6..81d936c 100644
--- a/include/bx/sem.h
+++ b/include/bx/sem.h
@@ -75,6 +75,14 @@ namespace bx
 			int result = pthread_mutex_lock(&m_mutex);
 			BX_CHECK(0 == result, "pthread_mutex_lock %d", result);
 
+#		if BX_PLATFORM_NACL || BX_PLATFORM_OSX
+			BX_CHECK(-1 == _msecs, "NaCl and OSX don't support pthread_cond_timedwait at this moment.");
+			while (0 == result
+			&&     0 >= m_count)
+			{
+				result = pthread_cond_wait(&m_cond, &m_mutex);
+			}
+#		else
 			timespec ts;
 			clock_gettime(CLOCK_REALTIME, &ts);
 			ts.tv_sec += _msecs/1000;
@@ -85,7 +93,7 @@ namespace bx
 			{
 				result = pthread_cond_timedwait(&m_cond, &m_mutex, &ts);
 			}
-
+#		endif // BX_PLATFORM_NACL || BX_PLATFORM_OSX
 			bool ok = 0 == result;
 
 			if (ok)