diff --git a/mypy/semanal.py b/mypy/semanal.py
index 7f961687a8ae..0e7cdae42673 100644
--- a/mypy/semanal.py
+++ b/mypy/semanal.py
@@ -4516,10 +4516,9 @@ def analyze_lvalue(
         elif isinstance(lval, TupleExpr):
             self.analyze_tuple_or_list_lvalue(lval, explicit_type)
         elif isinstance(lval, StarExpr):
-            if nested:
-                self.analyze_lvalue(lval.expr, nested, explicit_type)
-            else:
+            if not nested:
                 self.fail("Starred assignment target must be in a list or tuple", lval)
+            self.analyze_lvalue(lval.expr, nested, explicit_type)
         else:
             self.fail("Invalid assignment target", lval)
 
diff --git a/test-data/unit/check-statements.test b/test-data/unit/check-statements.test
index cb445cf4a1a2..f9156b4d1b8c 100644
--- a/test-data/unit/check-statements.test
+++ b/test-data/unit/check-statements.test
@@ -2104,6 +2104,12 @@ if int():
 -- ---------------
 
 
+[case testInvalidBareStarAssignmentTargetNoCrash]
+# https://github.com/python/mypy/issues/20796
+# flags: --debug-serialize
+*a = b  # E: Starred assignment target must be in a list or tuple \
+        # E: Name "b" is not defined
+
 [case testAssignListToStarExpr]
 from typing import List
 bs: List[A]