diff --git a/activemodel/lib/active_model/type/helpers/numeric.rb b/activemodel/lib/active_model/type/helpers/numeric.rb
index 8e989b286f1d3..6b3d2fb6f3f27 100644
--- a/activemodel/lib/active_model/type/helpers/numeric.rb
+++ b/activemodel/lib/active_model/type/helpers/numeric.rb
@@ -42,7 +42,8 @@ def equal_nan?(old_value, new_value)
           end
 
           def number_to_non_number?(old_value, new_value_before_type_cast)
-            old_value != nil && non_numeric_string?(new_value_before_type_cast.to_s)
+            old_value != nil && !new_value_before_type_cast.is_a?(::Numeric) &&
+              non_numeric_string?(new_value_before_type_cast.to_s)
           end
 
           def non_numeric_string?(value)
diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index b79cadba7cf68..e5677dc814b4a 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,9 @@
+*   Don't mark Float::INFINITY as changed when reassigning it
+
+    When saving a record with a float infinite value, it shouldn't mark as changed
+
+    *Maicol Bentancor*
+
 *   Support `RETURNING` clause for MariaDB
 
     *fatkodima*, *Nikolay Kondratyev*
diff --git a/activerecord/test/cases/adapters/postgresql/numbers_test.rb b/activerecord/test/cases/adapters/postgresql/numbers_test.rb
index 824d50ac988bf..a1e4a69b072f4 100644
--- a/activerecord/test/cases/adapters/postgresql/numbers_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/numbers_test.rb
@@ -48,4 +48,20 @@ def test_update
     assert_equal new_single, record.single
     assert_equal new_double, record.double
   end
+
+  def test_reassigning_infinity_does_not_mark_record_as_changed
+    record = PostgresqlNumber.create!(single: Float::INFINITY, double: -Float::INFINITY)
+    record.reload
+    record.single = Float::INFINITY
+    record.double = -Float::INFINITY
+    assert_not_predicate record, :changed?
+  end
+
+  def test_reassigning_nan_does_not_mark_record_as_changed
+    record = PostgresqlNumber.create!(single: Float::NAN, double: Float::NAN)
+    record.reload
+    record.single = Float::NAN
+    record.double = Float::NAN
+    assert_not_predicate record, :changed?
+  end
 end