diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 1234bb9a15d4dff99ec46f2247c16c9be667d0d7..c5945f3c3a169d25da7b62c2a21fd75c3fd6b6bc 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,7 @@
+*   Deprecate `map!` and `collect!` on `ActiveRecord::Result`.
+
+    *Ryuta Kamizono*
+
 *   Support `relation.and` for intersection as Set theory.
 
     ```ruby
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
index e016a6f032598a922d4765a8f662c9c10a1a82f3..0dcc8fd9f31a75b0e3bd7343b3dfa50da6044ce7 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
@@ -518,7 +518,7 @@ def table_structure_with_collation(table_name, basic_structure)
               collation_hash[$1] = $2 if COLLATE_REGEX =~ column_string
             end
 
-            basic_structure.map! do |column|
+            basic_structure.map do |column|
               column_name = column["name"]
 
               if collation_hash.has_key? column_name
diff --git a/activerecord/lib/active_record/result.rb b/activerecord/lib/active_record/result.rb
index 7e15a8e8e5d7a9452d190bee4ab88ecbc3073617..e0710266b4fbde346e301442c54300fbabfca9fc 100644
--- a/activerecord/lib/active_record/result.rb
+++ b/activerecord/lib/active_record/result.rb
@@ -75,6 +75,8 @@ def to_hash
 
     alias :map! :map
     alias :collect! :map
+    deprecate "map!": :map
+    deprecate "collect!": :map
 
     # Returns true if there are no records, otherwise false.
     def empty?
diff --git a/activerecord/test/cases/result_test.rb b/activerecord/test/cases/result_test.rb
index 4ac2097734af304994da2655d794d19d9508f90a..cf3da5b62efa7326b389c98aae969f90628ae598 100644
--- a/activerecord/test/cases/result_test.rb
+++ b/activerecord/test/cases/result_test.rb
@@ -12,6 +12,28 @@ def result
       ])
     end
 
+    test "map! is deprecated" do
+      assert_deprecated do
+        result.map! { nil }
+      end
+      assert_equal [
+        { "col_1" => "row 1 col 1", "col_2" => "row 1 col 2" },
+        { "col_1" => "row 2 col 1", "col_2" => "row 2 col 2" },
+        { "col_1" => "row 3 col 1", "col_2" => "row 3 col 2" },
+      ], result.to_a
+    end
+
+    test "collect! is deprecated" do
+      assert_deprecated do
+        result.collect! { nil }
+      end
+      assert_equal [
+        { "col_1" => "row 1 col 1", "col_2" => "row 1 col 2" },
+        { "col_1" => "row 2 col 1", "col_2" => "row 2 col 2" },
+        { "col_1" => "row 3 col 1", "col_2" => "row 3 col 2" },
+      ], result.to_a
+    end
+
     test "includes_column?" do
       assert result.includes_column?("col_1")
       assert_not result.includes_column?("foo")