diff --git a/mypy/nodes.py b/mypy/nodes.py
index 6487ee4b745c..10377eec07ba 100644
--- a/mypy/nodes.py
+++ b/mypy/nodes.py
@@ -2075,7 +2075,7 @@ class AssignmentExpr(Expression):
 
     __match_args__ = ("target", "value")
 
-    def __init__(self, target: Expression, value: Expression) -> None:
+    def __init__(self, target: NameExpr, value: Expression) -> None:
         super().__init__()
         self.target = target
         self.value = value
diff --git a/mypy/treetransform.py b/mypy/treetransform.py
index 3e5a7ef3f2ca..0abf98a52336 100644
--- a/mypy/treetransform.py
+++ b/mypy/treetransform.py
@@ -559,7 +559,7 @@ def visit_super_expr(self, node: SuperExpr) -> SuperExpr:
         return new
 
     def visit_assignment_expr(self, node: AssignmentExpr) -> AssignmentExpr:
-        return AssignmentExpr(self.expr(node.target), self.expr(node.value))
+        return AssignmentExpr(self.duplicate_name(node.target), self.expr(node.value))
 
     def visit_unary_expr(self, node: UnaryExpr) -> UnaryExpr:
         new = UnaryExpr(node.op, self.expr(node.expr))