diff --git a/imperative/python/megengine/quantization/observer.py b/imperative/python/megengine/quantization/observer.py
index f565f993..8b310586 100644
--- a/imperative/python/megengine/quantization/observer.py
+++ b/imperative/python/megengine/quantization/observer.py
@@ -201,7 +201,7 @@ class SyncExponentialMovingAverageObserver(ExponentialMovingAverageObserver):
     def forward(self, x_orig):
         if self.enabled:
             x = x_orig.detach()
-            if is_distributed:
+            if is_distributed():
                 min_x = all_reduce_min(x.min(), WORLD)
                 max_x = all_reduce_max(x.max(), WORLD)
             else: