diff --git a/libs/vkd3d/device.c b/libs/vkd3d/device.c
index 3c06cd0b..e826478f 100644
--- a/libs/vkd3d/device.c
+++ b/libs/vkd3d/device.c
@@ -1673,6 +1673,7 @@ static void STDMETHODCALLTYPE d3d12_device_CopyDescriptors(ID3D12Device *iface,
     struct d3d12_device *device = impl_from_ID3D12Device(iface);
     unsigned int dst_range_idx, dst_idx, src_range_idx, src_idx;
     const struct d3d12_desc *src;
+    unsigned int src_range_size;
     struct d3d12_desc *dst;
 
     TRACE("iface %p, dst_descriptor_range_count %u, dst_descriptor_range_offsets %p, "
@@ -1695,7 +1696,8 @@ static void STDMETHODCALLTYPE d3d12_device_CopyDescriptors(ID3D12Device *iface,
     for (src_range_idx = 0; src_range_idx < src_descriptor_range_count; ++src_range_idx)
     {
         src = d3d12_desc_from_cpu_handle(src_descriptor_range_offsets[src_range_idx]);
-        for (src_idx = 0; src_idx < src_descriptor_range_sizes[src_range_idx]; ++src_idx)
+        src_range_size = src_descriptor_range_sizes ? src_descriptor_range_sizes[src_range_idx] : 1;
+        for (src_idx = 0; src_idx < src_range_size; ++src_idx)
         {
             if (dst_idx >= dst_descriptor_range_sizes[dst_range_idx])
             {
diff --git a/tests/d3d12.c b/tests/d3d12.c
index c140a266..587f8b72 100644
--- a/tests/d3d12.c
+++ b/tests/d3d12.c
@@ -11413,16 +11413,12 @@ static void test_copy_descriptors(void)
     dst_handles[0] = get_cpu_sampler_handle(&context, sampler_heap, 0);
     dst_range_sizes[0] = 4;
     src_handles[0] = get_cpu_sampler_handle(&context, cpu_sampler_heap2, 0);
-    src_range_sizes[0] = 1;
     src_handles[1] = get_cpu_sampler_handle(&context, cpu_sampler_heap2, 0);
-    src_range_sizes[1] = 1;
     src_handles[2] = get_cpu_sampler_handle(&context, cpu_sampler_heap2, 0);
-    src_range_sizes[2] = 1;
     src_handles[3] = get_cpu_sampler_handle(&context, cpu_sampler_heap2, 1);
-    src_range_sizes[3] = 1;
     /* s0-s3 */
     ID3D12Device_CopyDescriptors(device, 1, dst_handles, dst_range_sizes,
-            4, src_handles, src_range_sizes, D3D12_DESCRIPTOR_HEAP_TYPE_SAMPLER);
+            4, src_handles, NULL, D3D12_DESCRIPTOR_HEAP_TYPE_SAMPLER);
 
     dst_handles[0] = get_cpu_descriptor_handle(&context, heap, 9);
     dst_range_sizes[0] = 4;