diff --git a/renderdoc/driver/d3d12/d3d12_device.cpp b/renderdoc/driver/d3d12/d3d12_device.cpp
index 2469ca924..ed6c5388e 100644
--- a/renderdoc/driver/d3d12/d3d12_device.cpp
+++ b/renderdoc/driver/d3d12/d3d12_device.cpp
@@ -916,8 +916,8 @@ bool WrappedID3D12Device::Serialise_MapDataWrite(Serialiser *localSerialiser,
 
       ID3D12Resource *uploadBuf = GetUploadBuffer(cmd.m_CurChunkOffset, end - begin);
 
-      SetObjName(uploadBuf, StringFormat::Fmt("Map data write, %llu bytes for %llu/%u @ %llu",
-                                              (begin - end), res, sub, cmd.m_CurChunkOffset));
+      SetObjName(uploadBuf, StringFormat::Fmt("Map() data write, %llu bytes for %llu/%u @ %llu",
+                                              (end - begin), res, sub, cmd.m_CurChunkOffset));
 
       // during reading, fill out the buffer itself
       if(m_State == READING)