diff --git a/implementations/Crafter.Graphics-RenderingElement3D.cpp b/implementations/Crafter.Graphics-RenderingElement3D.cpp
index e1754aa..21359d8 100644
--- a/implementations/Crafter.Graphics-RenderingElement3D.cpp
+++ b/implementations/Crafter.Graphics-RenderingElement3D.cpp
@@ -119,10 +119,15 @@ void RenderingElement3D::BuildTLAS(VkCommandBuffer cmd, std::uint32_t index, RTB
         // (no-op when the chosen type is coherent — the previous behaviour),
         // and the queue submit carries the host-write -> shader-read ordering as
         // it always has.
+        //
+        // At least one slot each: a TLAS built before anything is in the scene
+        // has zero instances, and a zero-size buffer is invalid (NVIDIA fails
+        // the allocation). The empty build reads no instance anyway.
         if (tlas.instanceBuffer.buffer == VK_NULL_HANDLE
             || primitiveCount > tlas.instanceBuffer.size / sizeof(VkAccelerationStructureInstanceKHR)) {
-            tlas.instanceBuffer.Resize(VK_BUFFER_USAGE_SHADER_DEVICE_ADDRESS_BIT | VK_BUFFER_USAGE_TRANSFER_DST_BIT | VK_BUFFER_USAGE_ACCELERATION_STRUCTURE_BUILD_INPUT_READ_ONLY_BIT_KHR | VK_BUFFER_USAGE_STORAGE_BUFFER_BIT, VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT, primitiveCount, VK_MEMORY_PROPERTY_DEVICE_LOCAL_BIT);
-            tlas.metadataBuffer.Resize(VK_BUFFER_USAGE_STORAGE_BUFFER_BIT | VK_BUFFER_USAGE_SHADER_DEVICE_ADDRESS_BIT, VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT, primitiveCount, VK_MEMORY_PROPERTY_DEVICE_LOCAL_BIT);
+            const std::uint32_t capacity = std::max(primitiveCount, 1u);
+            tlas.instanceBuffer.Resize(VK_BUFFER_USAGE_SHADER_DEVICE_ADDRESS_BIT | VK_BUFFER_USAGE_TRANSFER_DST_BIT | VK_BUFFER_USAGE_ACCELERATION_STRUCTURE_BUILD_INPUT_READ_ONLY_BIT_KHR | VK_BUFFER_USAGE_STORAGE_BUFFER_BIT, VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT, capacity, VK_MEMORY_PROPERTY_DEVICE_LOCAL_BIT);
+            tlas.metadataBuffer.Resize(VK_BUFFER_USAGE_STORAGE_BUFFER_BIT | VK_BUFFER_USAGE_SHADER_DEVICE_ADDRESS_BIT, VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT, capacity, VK_MEMORY_PROPERTY_DEVICE_LOCAL_BIT);
         }
 
         // A topology change reshuffles which element occupies each slot (a count
@@ -250,7 +255,9 @@ void RenderingElement3D::BuildTLAS(VkCommandBuffer cmd, std::uint32_t index, RTB
 
         // Scratch buffer must hold at least max(buildScratchSize, updateScratchSize).
         // Sizing for buildScratchSize covers both — refit is always smaller.
-        tlas.scratchBuffer.Resize(VK_BUFFER_USAGE_STORAGE_BUFFER_BIT | VK_BUFFER_USAGE_SHADER_DEVICE_ADDRESS_BIT, VK_MEMORY_PROPERTY_DEVICE_LOCAL_BIT, tlasBuildSizes.buildScratchSize);
+        // An empty TLAS may need no scratch at all, but the buffer can't be
+        // zero-size.
+        tlas.scratchBuffer.Resize(VK_BUFFER_USAGE_STORAGE_BUFFER_BIT | VK_BUFFER_USAGE_SHADER_DEVICE_ADDRESS_BIT, VK_MEMORY_PROPERTY_DEVICE_LOCAL_BIT, std::max<VkDeviceSize>(tlasBuildSizes.buildScratchSize, 1));
         tlas.buffer.Resize(VK_BUFFER_USAGE_ACCELERATION_STRUCTURE_STORAGE_BIT_KHR | VK_BUFFER_USAGE_SHADER_DEVICE_ADDRESS_BIT | VK_BUFFER_USAGE_ACCELERATION_STRUCTURE_BUILD_INPUT_READ_ONLY_BIT_KHR, VK_MEMORY_PROPERTY_DEVICE_LOCAL_BIT, tlasBuildSizes.accelerationStructureSize);
 
         // Destroy the previous AS handle before creating a new one — the