diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8f89b1fe1e..3ccd6897bf 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## master (unreleased)
 
+### Bug fixes
+
+* [#67](https://github.com/rubocop-hq/rubocop-performance/issues/67): Fix an error for `Performance/RedundantMerge` when `MaxKeyValuePairs` option is set to `null`. ([@koic][])
+
 ## 1.4.0 (2019-06-20)
 
 ### Bug fixes
diff --git a/lib/rubocop/cop/performance/redundant_merge.rb b/lib/rubocop/cop/performance/redundant_merge.rb
index 2e43734520..45b610846c 100644
--- a/lib/rubocop/cop/performance/redundant_merge.rb
+++ b/lib/rubocop/cop/performance/redundant_merge.rb
@@ -132,7 +132,7 @@ def indent_width
         end
 
         def max_key_value_pairs
-          Integer(cop_config['MaxKeyValuePairs'])
+          Integer(cop_config['MaxKeyValuePairs']) || 2
         end
 
         # A utility class for checking the use of values within an