diff --git a/src/main/java/org/codehaus/groovy/runtime/metaclass/ClosureMetaClass.java b/src/main/java/org/codehaus/groovy/runtime/metaclass/ClosureMetaClass.java
index 95495bba558..2d7332d3320 100644
--- a/src/main/java/org/codehaus/groovy/runtime/metaclass/ClosureMetaClass.java
+++ b/src/main/java/org/codehaus/groovy/runtime/metaclass/ClosureMetaClass.java
@@ -47,9 +47,12 @@
 import java.lang.reflect.Constructor;
 import java.lang.reflect.Method;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 /**
  * A metaclass for closures generated by the Groovy compiler. These classes
@@ -372,17 +375,9 @@ private static Object invokeOnDelegationObject(final Class sender, final Object
         throw first;
     }
 
+    private static final Set<String> INTERNAL_METHODS = new HashSet<>(Arrays.asList("curry", "ncurry", "rcurry", "leftShift", "rightShift"));
     private static boolean isInternalMethod(final String methodName) {
-        switch (methodName) {
-          case "curry":
-          case "ncurry":
-          case "rcurry":
-          case "leftShift":
-          case "rightShift":
-            return true;
-          default:
-            return false;
-        }
+        return INTERNAL_METHODS.contains(methodName);
     }
 
     private synchronized void initAttributes() {