diff --git a/util/test/demos/d3d12/d3d12_cbuffer_zoo.cpp b/util/test/demos/d3d12/d3d12_cbuffer_zoo.cpp
index 4cfc8dd05..549b770af 100644
--- a/util/test/demos/d3d12/d3d12_cbuffer_zoo.cpp
+++ b/util/test/demos/d3d12/d3d12_cbuffer_zoo.cpp
@@ -238,9 +238,14 @@ cbuffer rootconsts : register(b1)
   float3_1 root_d;
 };
 
+cbuffer hugespace : register(b0, space999999999)
+{
+  float4 huge_val;
+};
+
 float4 main() : SV_Target0
 {
-	return test + root_zero + float4(0.1f, 0.0f, 0.0f, 0.0f);
+	return test + root_zero + huge_val * 1e-30f + float4(0.1f, 0.0f, 0.0f, 0.0f);
 }
 
 )EOSHADER";
@@ -266,7 +271,7 @@ float4 main() : SV_Target0
       return 3;
 
     ID3DBlobPtr vsblob = Compile(D3DDefaultVertex, "main", "vs_5_0");
-    ID3DBlobPtr psblob = Compile(pixel, "main", "ps_5_0");
+    ID3DBlobPtr psblob = Compile(pixel, "main", "ps_5_1");
 
     Vec4f cbufferdata[512];
 
@@ -299,6 +304,7 @@ float4 main() : SV_Target0
     ID3D12RootSignaturePtr sig = MakeSig({
         cbvParam(D3D12_SHADER_VISIBILITY_PIXEL, 0, 0),
         constParam(D3D12_SHADER_VISIBILITY_PIXEL, 0, 1, sizeof(rootData) / sizeof(uint32_t)),
+        cbvParam(D3D12_SHADER_VISIBILITY_PIXEL, 999999999, 0),
     });
 
     ID3D12PipelineStatePtr pso = MakePSO().RootSig(sig).InputLayout().VS(vsblob).PS(psblob).RTVs(
@@ -335,6 +341,7 @@ float4 main() : SV_Target0
       cmd->SetGraphicsRootSignature(sig);
       cmd->SetGraphicsRootConstantBufferView(0, cb->GetGPUVirtualAddress());
       cmd->SetGraphicsRoot32BitConstants(1, sizeof(rootData) / sizeof(uint32_t), &rootData, 0);
+      cmd->SetGraphicsRootConstantBufferView(2, cb->GetGPUVirtualAddress() + 256);
 
       RSSetViewport(cmd, {0.0f, 0.0f, (float)screenWidth, (float)screenHeight, 0.0f, 1.0f});
       RSSetScissorRect(cmd, {0, 0, screenWidth, screenHeight});
diff --git a/util/test/tests/D3D12/D3D12_CBuffer_Zoo.py b/util/test/tests/D3D12/D3D12_CBuffer_Zoo.py
index 9b193895b..ab3a0a6e3 100644
--- a/util/test/tests/D3D12/D3D12_CBuffer_Zoo.py
+++ b/util/test/tests/D3D12/D3D12_CBuffer_Zoo.py
@@ -15,6 +15,28 @@ class D3D12_CBuffer_Zoo(rdtest.TestCase):
         pipe: rd.PipeState = self.controller.GetPipelineState()
 
         stage = rd.ShaderStage.Pixel
+
+        refl: rd.ShaderReflection = pipe.GetShaderReflection(stage)
+        mapping: rd.ShaderBindpointMapping = pipe.GetBindpointMapping(stage)
+
+        # Make sure we have three constant buffers - b0 normal, b1 root constants, and space9999999:b0
+        binds = [
+            (0, 0),
+            (0, 1),
+            (999999999, 0),
+        ]
+
+        if len(refl.constantBlocks) != len(mapping.constantBlocks) or len(refl.constantBlocks) != len(binds):
+            raise rdtest.TestFailureException(
+                "Expected {}} constant buffers, only got {} {}".format(len(binds), len(refl.constantBlocks),
+                                                                       len(refl.constantBlocks)))
+
+        for b in range(0, len(binds)):
+            if binds[b][0] != mapping.constantBlocks[b].bindset or binds[b][1] != mapping.constantBlocks[b].bind:
+                raise rdtest.TestFailureException(
+                    "Unexpected cb[{}] mapping: set {} bind {}".format(b, mapping.constantBlocks[b].bindset,
+                                                                       mapping.constantBlocks[b].bind))
+
         cbuf: rd.BoundCBuffer = pipe.GetConstantBuffer(stage, 0, 0)
 
         var_check = rdtest.ConstantBufferChecker(
@@ -340,3 +362,14 @@ class D3D12_CBuffer_Zoo(rdtest.TestCase):
         var_check.done()
 
         rdtest.log.success("Root signature variables are as expected")
+
+        cbuf: rd.BoundCBuffer = pipe.GetConstantBuffer(stage, 2, 0)
+
+        var_check = rdtest.ConstantBufferChecker(
+            self.controller.GetCBufferVariableContents(pipe.GetGraphicsPipelineObject(),
+                                                       pipe.GetShader(stage),
+                                                       pipe.GetShaderEntryPoint(stage), 2,
+                                                       cbuf.resourceId, cbuf.byteOffset))
+
+        # float4 huge_val;
+        var_check.check('huge_val').rows(1).cols(4).value([64.0, 65.0, 66.0, 67.0])