diff --git a/src/libsysprof/sysprof-callgraph-private.h b/src/libsysprof/sysprof-callgraph-private.h
index b4d7ad3a..217dd6c2 100644
--- a/src/libsysprof/sysprof-callgraph-private.h
+++ b/src/libsysprof/sysprof-callgraph-private.h
@@ -47,7 +47,8 @@ struct _SysprofCallgraphNode
   SysprofCallgraphNode     *children;
   SysprofCallgraphSummary  *summary;
   gpointer                  augment[2];
-  SysprofCallgraphCategory  category;
+  SysprofCallgraphCategory  category : 7;
+  SysprofCallgraphCategory  is_toplevel : 7;
 };
 
 struct _SysprofCallgraph
diff --git a/src/libsysprof/sysprof-callgraph.c b/src/libsysprof/sysprof-callgraph.c
index 9055f846..ec2bca0f 100644
--- a/src/libsysprof/sysprof-callgraph.c
+++ b/src/libsysprof/sysprof-callgraph.c
@@ -191,6 +191,8 @@ sysprof_callgraph_populate_callers (SysprofCallgraph     *self,
   g_assert (SYSPROF_IS_CALLGRAPH (self));
   g_assert (node != NULL);
 
+  node->is_toplevel = TRUE;
+
   for (const SysprofCallgraphNode *iter = node;
        iter != NULL;
        iter = iter->parent)
diff --git a/src/libsysprof/sysprof-descendants-model.c b/src/libsysprof/sysprof-descendants-model.c
index e7f6c1f8..3507c2e3 100644
--- a/src/libsysprof/sysprof-descendants-model.c
+++ b/src/libsysprof/sysprof-descendants-model.c
@@ -210,6 +210,8 @@ sysprof_descendants_model_add_traceable (SysprofDescendantsModel  *self,
 
       node = sysprof_descendants_model_add_trace (self, symbols, n_symbols);
 
+      node->is_toplevel = TRUE;
+
       if (node && self->callgraph->augment_func)
         self->callgraph->augment_func (self->callgraph,
                                        node,