diff --git a/src/bgfx_p.h b/src/bgfx_p.h
index 52c0187d4..6a6e31d61 100644
--- a/src/bgfx_p.h
+++ b/src/bgfx_p.h
@@ -3454,6 +3454,8 @@ namespace bgfx
 
 		BGFX_API_FUNC(void allocInstanceDataBuffer(InstanceDataBuffer* _idb, uint32_t _num, uint16_t _stride) )
 		{
+			BGFX_MUTEX_SCOPE(m_resourceApiLock);
+
 			uint16_t stride = BX_ALIGN_16(_stride);
 			uint32_t offset = m_submit->allocTransientVertexBuffer(_num, stride);