diff --git a/.rubocop.yml b/.rubocop.yml
index a3ccce57..27712bd8 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -1,5 +1,10 @@
 inherit_from: .rubocop_todo.yml
 
+# Set this to the minimum supported ruby in the gemspec. Otherwise
+# we get errors if our ruby version doesn't match.
+AllCops:
+  TargetRubyVersion: 2.4
+
 Layout/HashAlignment:
   EnforcedHashRocketStyle: table
   EnforcedColonStyle: table