diff --git a/mypy/expandtype.py b/mypy/expandtype.py
index 5790b717172a..ea0e1e0d9ac4 100644
--- a/mypy/expandtype.py
+++ b/mypy/expandtype.py
@@ -223,7 +223,7 @@ def visit_instance(self, t: Instance) -> Type:
             # See: https://github.com/python/mypy/issues/16649
             return t.copy_modified(args=args)
 
-        if t.type.fullname == "builtins.tuple":
+        if t.type.fullname == "builtins.tuple" and len(args) > 0:
             # Normalize Tuple[*Tuple[X, ...], ...] -> Tuple[X, ...]
             arg = args[0]
             if isinstance(arg, UnpackType):
diff --git a/test-data/unit/check-python312.test b/test-data/unit/check-python312.test
index 0521722b47c1..986b24c74cf3 100644
--- a/test-data/unit/check-python312.test
+++ b/test-data/unit/check-python312.test
@@ -2237,3 +2237,17 @@ class D[*Ts](Generic[Unpack[Us]]):  # E: Generic[...] base class is redundant \
                                     # E: Can only use one type var tuple in a class def
     pass
 [builtins fixtures/tuple.pyi]
+
+[case testUnpackEmptyTupleInTypeAliasNoCrash]
+# https://github.com/python/mypy/issues/20913
+from typing import Unpack
+
+class C[*Ts]:
+    pass
+
+type T[T, *Ts] = C[*Ts]
+
+x: T[bool, Unpack[tuple[()]]]
+reveal_type(x)  # N: Revealed type is "__main__.C[Unpack[builtins.tuple]]"
+[builtins fixtures/tuple.pyi]
+[typing fixtures/typing-full.pyi]