diff --git a/python_module/megengine/_internal/comp_graph_tools.py b/python_module/megengine/_internal/comp_graph_tools.py
index bbbd3ef24aff2717354f678e49dc45f9a8edf295..19223d072cff7b3a0deae57ee6a397bb22fa1272 100644
--- a/python_module/megengine/_internal/comp_graph_tools.py
+++ b/python_module/megengine/_internal/comp_graph_tools.py
@@ -25,7 +25,7 @@ def get_dep_vars(var, var_type=None):
     outputs = []
     memo = set()
 
-    if not isinstance(var, collections.Iterable):
+    if isinstance(var, _mgb.SymbolVar):
         var = [var]
 
     if isinstance(var_type, str):