diff --git a/python/taichi/lang/expr.py b/python/taichi/lang/expr.py
index 6e978b0b17f320..6da9e879e9c980 100644
--- a/python/taichi/lang/expr.py
+++ b/python/taichi/lang/expr.py
@@ -46,16 +46,16 @@ def stack_info():
         # remove the confusing last line
         return '\n'.join(raw.split('\n')[:-3]) + '\n'
 
+    def __neg__(self):
+        import taichi as ti
+        return ti.neg(self)
+
     def __add__(self, other):
         import taichi as ti
         return ti.add(self, other)
 
     __radd__ = __add__
 
-    def __neg__(self):
-        import taichi as ti
-        return ti.neg(self)
-
     def __sub__(self, other):
         import taichi as ti
         return ti.sub(self, other)