diff --git a/compiler/guards.nim b/compiler/guards.nim
index bbb2398674..553cc744df 100644
--- a/compiler/guards.nim
+++ b/compiler/guards.nim
@@ -1165,8 +1165,12 @@ proc buildProperFieldCheck(access, check: PNode; o: Operators): PNode =
   if check[1].kind == nkCurly:
     result = copyTree(check)
     if access.kind == nkDotExpr:
+      # change the access to the discriminator field access
       var a = copyTree(access)
+      # set field name to discriminator field name
       a[1] = check[2]
+      # set discriminator field type: important for `neg`
+      a.typ = check[2].typ
       result[2] = a
       # 'access.kind != nkDotExpr' can happen for object constructors
       # which we don't check yet
diff --git a/tests/objvariant/tcorrectcheckedfield.nim b/tests/objvariant/tcorrectcheckedfield.nim
new file mode 100644
index 0000000000..e5e67c727d
--- /dev/null
+++ b/tests/objvariant/tcorrectcheckedfield.nim
@@ -0,0 +1,22 @@
+discard """
+  matrix: "; --warning[ProveField]:on --warningAsError[ProveField]:on; --experimental:strictCaseObjects"
+"""
+
+block: # issue #24021
+  type
+    FooKind = enum
+      a
+      b
+    BiggerEnum = enum b1, b2, b3, b4, b5, b6, b7, b8, b9, b10
+    Foo = object
+      case kind: FooKind
+      of a: discard
+      else:
+        z: BiggerEnum
+
+  proc p(foo: Foo, val: int) =
+    case foo.kind
+    of a:
+      discard
+    else:
+      discard foo.z