diff --git a/python/xorbits/_mars/dataframe/base/cartesian_chunk.py b/python/xorbits/_mars/dataframe/base/cartesian_chunk.py
index 30db54e1d..774f6747f 100644
--- a/python/xorbits/_mars/dataframe/base/cartesian_chunk.py
+++ b/python/xorbits/_mars/dataframe/base/cartesian_chunk.py
@@ -139,9 +139,10 @@ def tile(cls, op: "DataFrameCartesianChunk"):
         auto_merge_threshold = op.auto_merge_threshold
         auto_merge_before, auto_merge_after = cls._get_auto_merge_options(op.auto_merge)
 
-        yield from cls._merge_before(
+        merge_before_res = yield from cls._merge_before(
             op, auto_merge_before, auto_merge_threshold, left, right, logger
         )
+        left, right = merge_before_res[0], merge_before_res[1]
 
         if left.ndim == 2 and left.chunk_shape[1] > 1:
             if has_unknown_shape(left):
diff --git a/python/xorbits/_mars/dataframe/base/core.py b/python/xorbits/_mars/dataframe/base/core.py
index 5f444c439..57796babc 100644
--- a/python/xorbits/_mars/dataframe/base/core.py
+++ b/python/xorbits/_mars/dataframe/base/core.py
@@ -128,6 +128,7 @@ def _merge_before(
                 right.shape,
                 len(right.chunks),
             )
+        return [left, right]
 
     @classmethod
     def _merge_after(
diff --git a/python/xorbits/_mars/dataframe/merge/merge.py b/python/xorbits/_mars/dataframe/merge/merge.py
index 8f1baf5e5..4db6993aa 100644
--- a/python/xorbits/_mars/dataframe/merge/merge.py
+++ b/python/xorbits/_mars/dataframe/merge/merge.py
@@ -744,9 +744,10 @@ def tile(cls, op: "DataFrameMerge"):
         auto_merge_threshold = op.auto_merge_threshold
         auto_merge_before, auto_merge_after = cls._get_auto_merge_options(op.auto_merge)
 
-        yield from cls._merge_before(
+        merge_before_res = yield from cls._merge_before(
             op, auto_merge_before, auto_merge_threshold, left, right, logger
         )
+        left, right = merge_before_res[0], merge_before_res[1]
 
         method = cls._choose_merge_method(op, left, right)
         if cls._if_apply_bloom_filter(method, op, left, right):