diff --git a/changelog/change_mark_rails_index_with_as_unsafe.md b/changelog/change_mark_rails_index_with_as_unsafe.md
new file mode 100644
index 0000000000..97631970a7
--- /dev/null
+++ b/changelog/change_mark_rails_index_with_as_unsafe.md
@@ -0,0 +1 @@
+* [#1463](https://github.com/rubocop/rubocop-rails/pull/1463): Mark `Rails/IndexWith` as unsafe autocorrect. ([@tejasbubane][])
diff --git a/config/default.yml b/config/default.yml
index cd1a0e9833..6dab61fce2 100644
--- a/config/default.yml
+++ b/config/default.yml
@@ -647,8 +647,9 @@ Rails/IndexBy:
 Rails/IndexWith:
   Description: 'Prefer `index_with` over `each_with_object`, `to_h`, or `map`.'
   Enabled: true
+  SafeAutoCorrect: false
   VersionAdded: '2.5'
-  VersionChanged: '2.8'
+  VersionChanged: '<<next>>'
 
 Rails/Inquiry:
   Description: "Prefer Ruby's comparison operators over Active Support's `Array#inquiry` and `String#inquiry`."
diff --git a/lib/rubocop/cop/rails/index_with.rb b/lib/rubocop/cop/rails/index_with.rb
index fc72c51646..337f09c4f6 100644
--- a/lib/rubocop/cop/rails/index_with.rb
+++ b/lib/rubocop/cop/rails/index_with.rb
@@ -8,6 +8,10 @@ module Rails
       # an enumerable into a hash where the keys are the original elements.
       # Rails provides the `index_with` method for this purpose.
       #
+      # This cop is marked as unsafe autocorrection, because `nil.to_h` returns {}
+      # but `nil.with_index` throws `NoMethodError`. Therefore, autocorrection is not
+      # compatible if the receiver is nil.
+      #
       # @example
       #   # bad
       #   [1, 2, 3].each_with_object({}) { |el, h| h[el] = foo(el) }