diff --git a/renderdoc/driver/d3d11/d3d11_context.cpp b/renderdoc/driver/d3d11/d3d11_context.cpp
index 46b702e69..de7bd946f 100644
--- a/renderdoc/driver/d3d11/d3d11_context.cpp
+++ b/renderdoc/driver/d3d11/d3d11_context.cpp
@@ -1341,7 +1341,7 @@ void WrappedID3D11DeviceContext::FlattenLog()
     }
   }
 
-  m_pSerialiser = new Serialiser(dst->GetSize(), dst->GetRawPtr(0), false);
+  m_pSerialiser = new Serialiser((size_t)dst->GetSize(), dst->GetRawPtr(0), false);
   m_OwnSerialiser = true;
 
   m_pSerialiser->SetDebugText(true);