diff --git a/mypy/checker.py b/mypy/checker.py
index 159569849061..7579c36a97d0 100644
--- a/mypy/checker.py
+++ b/mypy/checker.py
@@ -2188,7 +2188,14 @@ def check_method_override_for_base_with_name(
         else:
             override_class_or_static = defn.func.is_class or defn.func.is_static
         typ, _ = self.node_type_from_base(defn.name, defn.info, defn)
-        assert typ is not None
+        if typ is None:
+            # This may only happen if we're checking `x-redefinition` member
+            # and `x` itself is for some reason gone. Normally the node should
+            # be reachable from the containing class by its name.
+            # The redefinition is never removed, use this as a sanity check to verify
+            # the reasoning above.
+            assert f"{defn.name}-redefinition" in defn.info.names
+            return False
 
         original_node = base_attr.node
         # `original_type` can be partial if (e.g.) it is originally an
diff --git a/test-data/unit/check-dataclasses.test b/test-data/unit/check-dataclasses.test
index 2ead202bd6af..a6ac30e20c36 100644
--- a/test-data/unit/check-dataclasses.test
+++ b/test-data/unit/check-dataclasses.test
@@ -2666,3 +2666,19 @@ class PersonBad(TypedDict):
 class JobBad:
     person: PersonBad = field(default_factory=PersonBad)  # E: Argument "default_factory" to "field" has incompatible type "type[PersonBad]"; expected "Callable[[], PersonBad]"
 [builtins fixtures/dict.pyi]
+
+[case testDataclassInitVarRedefinitionNoCrash]
+# https://github.com/python/mypy/issues/19443
+from dataclasses import InitVar, dataclass
+
+class ClassA:
+    def value(self) -> int:
+        return 0
+
+@dataclass
+class ClassB(ClassA):
+    value: InitVar[int]
+
+    def value(self) -> int:  # E: Name "value" already defined on line 10
+        return 0
+[builtins fixtures/dict.pyi]