diff --git a/renderdoc/driver/d3d12/d3d12_debug.cpp b/renderdoc/driver/d3d12/d3d12_debug.cpp
index 25bc48ec8..777abfa71 100644
--- a/renderdoc/driver/d3d12/d3d12_debug.cpp
+++ b/renderdoc/driver/d3d12/d3d12_debug.cpp
@@ -374,6 +374,7 @@ D3D12DebugManager::D3D12DebugManager(WrappedID3D12Device *wrapper)
   // VS CBV
   param.ShaderVisibility = D3D12_SHADER_VISIBILITY_VERTEX;
   param.ParameterType = D3D12_ROOT_PARAMETER_TYPE_CBV;
+  param.Descriptor.RegisterSpace = 0;
   param.Descriptor.ShaderRegister = 0;
   param.Descriptor.Flags = D3D12_ROOT_DESCRIPTOR_FLAG_NONE;
 
@@ -458,6 +459,7 @@ D3D12DebugManager::D3D12DebugManager(WrappedID3D12Device *wrapper)
   // 0: CBV
   param.ShaderVisibility = D3D12_SHADER_VISIBILITY_ALL;
   param.ParameterType = D3D12_ROOT_PARAMETER_TYPE_CBV;
+  param.Descriptor.RegisterSpace = 0;
   param.Descriptor.ShaderRegister = 0;
   param.Descriptor.Flags = D3D12_ROOT_DESCRIPTOR_FLAG_NONE;
 
@@ -506,6 +508,7 @@ D3D12DebugManager::D3D12DebugManager(WrappedID3D12Device *wrapper)
   // 0: CBV
   param.ShaderVisibility = D3D12_SHADER_VISIBILITY_PIXEL;
   param.ParameterType = D3D12_ROOT_PARAMETER_TYPE_CBV;
+  param.Descriptor.RegisterSpace = 0;
   param.Descriptor.ShaderRegister = 0;
   param.Descriptor.Flags = D3D12_ROOT_DESCRIPTOR_FLAG_NONE;
 
@@ -535,6 +538,7 @@ D3D12DebugManager::D3D12DebugManager(WrappedID3D12Device *wrapper)
   // 0: CBV
   param.ShaderVisibility = D3D12_SHADER_VISIBILITY_ALL;
   param.ParameterType = D3D12_ROOT_PARAMETER_TYPE_CBV;
+  param.Descriptor.RegisterSpace = 0;
   param.Descriptor.ShaderRegister = 0;
   param.Descriptor.Flags = D3D12_ROOT_DESCRIPTOR_FLAG_NONE;
 
diff --git a/renderdoc/driver/d3d12/d3d12_manager.cpp b/renderdoc/driver/d3d12/d3d12_manager.cpp
index d53207268..085df5305 100644
--- a/renderdoc/driver/d3d12/d3d12_manager.cpp
+++ b/renderdoc/driver/d3d12/d3d12_manager.cpp
@@ -899,14 +899,14 @@ bool D3D12ResourceManager::Serialise_InitialState(ResourceId resid, ID3D12Device
 
       byte dummy[4] = {};
       byte *ptr = NULL;
-      size_t size = 0;
+      uint64_t size = 0;
 
       HRESULT hr = E_NOINTERFACE;
 
       if(copiedBuffer)
       {
         hr = copiedBuffer->Map(0, NULL, (void **)&ptr);
-        size = (size_t)copiedBuffer->GetDesc().Width;
+        size = (uint64_t)copiedBuffer->GetDesc().Width;
       }
 
       if(FAILED(hr) || ptr == NULL)
@@ -918,7 +918,8 @@ bool D3D12ResourceManager::Serialise_InitialState(ResourceId resid, ID3D12Device
       }
 
       m_pSerialiser->Serialise("NumBytes", size);
-      m_pSerialiser->SerialiseBuffer("BufferData", ptr, size);
+      size_t sz = (size_t)size;
+      m_pSerialiser->SerialiseBuffer("BufferData", ptr, sz);
 
       if(SUCCEEDED(hr) && ptr)
         copiedBuffer->Unmap(0, NULL);