diff --git a/util/test/rdtest/analyse.py b/util/test/rdtest/analyse.py
index 51f69a755..a6af2e2be 100644
--- a/util/test/rdtest/analyse.py
+++ b/util/test/rdtest/analyse.py
@@ -74,7 +74,7 @@ def fetch_indices(controller: rd.ReplayController, mesh: rd.MeshFormat, index_of
                                           mesh.indexByteStride*num_indices)
 
         # Unpack all the indices
-        indices = struct.unpack(index_fmt, ibdata)
+        indices = struct.unpack_from(index_fmt, ibdata)
 
         # Apply the baseVertex offset
         return [i + mesh.baseVertex for i in indices]
@@ -88,7 +88,7 @@ class MeshAttribute:
     name: str
 
 
-def get_vsin_attrs(controller: rd.ReplayController, index_mesh: rd.MeshFormat):
+def get_vsin_attrs(controller: rd.ReplayController, vertexOffset: int, index_mesh: rd.MeshFormat):
     pipe: rd.PipeState = controller.GetPipelineState()
     inputs: List[rd.VertexInputAttribute] = pipe.GetVertexInputs()
 
@@ -107,7 +107,7 @@ def get_vsin_attrs(controller: rd.ReplayController, index_mesh: rd.MeshFormat):
         attr.mesh.instStepRate = a.instanceRate
         attr.mesh.instanced = a.perInstance
         attr.mesh.vertexResourceId = vbs[a.vertexBuffer].resourceId
-        attr.mesh.vertexByteOffset = vbs[a.vertexBuffer].byteOffset + a.byteOffset
+        attr.mesh.vertexByteOffset = vbs[a.vertexBuffer].byteOffset + a.byteOffset + vertexOffset * attr.mesh.vertexByteStride
 
         attr.mesh.format = a.format
 
diff --git a/util/test/rdtest/testcase.py b/util/test/rdtest/testcase.py
index 5b2f7a9c3..28e1e6c21 100644
--- a/util/test/rdtest/testcase.py
+++ b/util/test/rdtest/testcase.py
@@ -266,7 +266,12 @@ class TestCase:
         mesh.indexResourceId = ib.resourceId
         mesh.baseVertex = draw.baseVertex
 
-        attrs = analyse.get_vsin_attrs(self.controller, mesh)
+        if not (draw.flags & rd.DrawFlags.Indexed):
+            mesh.indexByteOffset = 0
+            mesh.indexByteStride = 0
+            mesh.indexResourceId = rd.ResourceId.Null()
+
+        attrs = analyse.get_vsin_attrs(self.controller, draw.vertexOffset, mesh)
 
         first_index = min(first_index, draw.numIndices-1)