diff --git a/Lib/dataclasses.py b/Lib/dataclasses.py
index 96bf6e1..ad7bf0f 100644
--- a/Lib/dataclasses.py
+++ b/Lib/dataclasses.py
@@ -1173,6 +1173,9 @@
             continue
 
         if f.name not in changes:
+            if f._field_type is _FIELD_INITVAR:
+                raise ValueError(f"InitVar {f.name!r} "
+                                 'must be specified with replace()')
             changes[f.name] = getattr(obj, f.name)
 
     # Create the new object, which calls __init__() and