diff --git a/taichi/analysis/alias_analysis.cpp b/taichi/analysis/alias_analysis.cpp
index c24d5acf5f31d1..f9d4b71e02db55 100644
--- a/taichi/analysis/alias_analysis.cpp
+++ b/taichi/analysis/alias_analysis.cpp
@@ -69,9 +69,9 @@ AliasResult alias_analysis(Stmt *var1, Stmt *var2) {
       // ExternalPtrStmt as its origin If not, the pointers are not aliased
       if (auto *matrix_ptr = other->cast<MatrixPtrStmt>()) {
         external_ptr = matrix_ptr->origin->cast<ExternalPtrStmt>();
-        if (!external_ptr)
-          return AliasResult::different;
       }
+      if (!external_ptr)
+          return AliasResult::different;
     }
     // If one external pointer references the grad tensor and the other
     // references the data tensor, they are not aliased