diff --git a/src/libsysprof/sysprof-callgraph-private.h b/src/libsysprof/sysprof-callgraph-private.h
index 5e588be9..b80c8283 100644
--- a/src/libsysprof/sysprof-callgraph-private.h
+++ b/src/libsysprof/sysprof-callgraph-private.h
@@ -71,6 +71,8 @@ struct _SysprofCallgraph
   GDestroyNotify           augment_func_data_destroy;
 
   SysprofCallgraphNode     root;
+
+  guint                    height;
 };
 
 void                      _sysprof_callgraph_new_async          (SysprofDocument          *document,
diff --git a/src/libsysprof/sysprof-callgraph.c b/src/libsysprof/sysprof-callgraph.c
index b7419f46..a8ef4736 100644
--- a/src/libsysprof/sysprof-callgraph.c
+++ b/src/libsysprof/sysprof-callgraph.c
@@ -421,6 +421,9 @@ sysprof_callgraph_add_traceable (SysprofCallgraph         *self,
   symbols[n_symbols++] = _sysprof_document_process_symbol (self->document, pid);
   symbols[n_symbols++] = everything;
 
+  if (n_symbols > self->height)
+    self->height = n_symbols;
+
   node = sysprof_callgraph_add_trace (self,
                                       symbols,
                                       n_symbols,