diff --git a/src/bgfx_p.h b/src/bgfx_p.h
index 3f95b7c1..c6f9b8bf 100755
--- a/src/bgfx_p.h
+++ b/src/bgfx_p.h
@@ -3091,7 +3091,8 @@ namespace bgfx
 		{
 // 			BX_TRACE("game wait");
 			int64_t start = bx::getHPCounter();
-			m_gameSem.wait();
+			bool ok = m_gameSem.wait();
+			BX_CHECK(ok, "Semaphore wait failed."); BX_UNUSED(ok);
 			m_render->m_waitSubmit = bx::getHPCounter()-start;
 		}
 
@@ -3105,7 +3106,8 @@ namespace bgfx
 		{
 // 			BX_TRACE("render wait");
 			int64_t start = bx::getHPCounter();
-			m_renderSem.wait();
+			bool ok = m_renderSem.wait();
+			BX_CHECK(ok, "Semaphore wait failed."); BX_UNUSED(ok);
 			m_submit->m_waitRender = bx::getHPCounter() - start;
 		}
 
diff --git a/src/renderer_gl.h b/src/renderer_gl.h
index 295ee548..9e4b03a3 100755
--- a/src/renderer_gl.h
+++ b/src/renderer_gl.h
@@ -443,6 +443,7 @@ namespace bgfx
 
 		void update(uint32_t _offset, uint32_t _size, void* _data)
 		{
+			BX_CHECK(0 != m_id, "Updating invalid index buffer.");
 			GL_CHECK(glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_id) );
 			GL_CHECK(glBufferSubData(GL_ELEMENT_ARRAY_BUFFER
 				, _offset
@@ -484,6 +485,7 @@ namespace bgfx
 
 		void update(uint32_t _offset, uint32_t _size, void* _data)
 		{
+			BX_CHECK(0 != m_id, "Updating invalid vertex buffer.");
 			GL_CHECK(glBindBuffer(GL_ARRAY_BUFFER, m_id) );
 			GL_CHECK(glBufferSubData(GL_ARRAY_BUFFER
 				, _offset