diff --git a/modules/library/main/src/main/java/org/geotools/filter/FunctionImpl.java b/modules/library/main/src/main/java/org/geotools/filter/FunctionImpl.java
index cdceb5d..d6166cb 100644
--- a/modules/library/main/src/main/java/org/geotools/filter/FunctionImpl.java
+++ b/modules/library/main/src/main/java/org/geotools/filter/FunctionImpl.java
@@ -131,9 +131,38 @@ public class FunctionImpl extends ExpressionAbstract implements Function {
     }
     
     /**
-     * Gathers up and groups the parameters to the function based on the declared parameters. 
+     * Validates the structure of arguments, basically enforcing java conventions for variable 
+     * level arguments.
      */
-    protected LinkedHashMap<String, Object> prepArguments(Object obj) {
+    private void validateArguments() {
+        List<Parameter<?>> args = getFunctionName().getArguments();
+        
+        for (int i = 0; i < args.size(); i++) {
+            Parameter<?> arg = args.get(i);
+            if (arg.getMaxOccurs() == 0) {
+                throw new IllegalArgumentException(String.format("Argument %s has zero max"));
+            }
+            if (arg.getMinOccurs() != 1 || arg.getMaxOccurs() != 1) {
+                //this can only happen for the last argument
+                if (i != args.size()-1) {
+                    throw new IllegalArgumentException(String.format("Argument %s(%d,%d) invalid." +
+                        " Variable arguments must be the last argument of function.", 
+                    arg.getName(), arg.getMinOccurs(), arg.getMaxOccurs()));
+                }
+            }
+        }
+    }
+
+    /**
+     * Gathers up and groups the parameters to the function based on the declared parameters.
+     * <p>
+     * This method calls {@link #validateArguments()} which enforces java style argument conventions
+     * for multi valued parameters. Basically enforcing that only teh last argument in a function 
+     * can be variable.
+     * </p>
+     *
+     */
+    protected LinkedHashMap<String, Object> dispatchArguments(Object obj) {
         LinkedHashMap<String, Object> prepped = new LinkedHashMap<String, Object>();
         
         List<Parameter<?>> args = getFunctionName().getArguments();
diff --git a/modules/library/main/src/main/java/org/geotools/filter/capability/FunctionNameImpl.java b/modules/library/main/src/main/java/org/geotools/filter/capability/FunctionNameImpl.java
index 8138547..a481f29 100644
--- a/modules/library/main/src/main/java/org/geotools/filter/capability/FunctionNameImpl.java
+++ b/modules/library/main/src/main/java/org/geotools/filter/capability/FunctionNameImpl.java
@@ -69,7 +69,6 @@ public class FunctionNameImpl extends OperatorImpl implements FunctionName {
         super( copy );
         this.ret = copy.getReturn();
         this.args = copy.getArguments();
-        validate();
     }
     
     public FunctionNameImpl( String name, Parameter<?> retern, Parameter<?>... arguments) {
@@ -80,7 +79,6 @@ public class FunctionNameImpl extends OperatorImpl implements FunctionName {
         super(name);
         this.ret = retern;
         this.args = arguments;
-        validate();
     }
     
     public int getArgumentCount() {
@@ -133,27 +131,6 @@ public class FunctionNameImpl extends OperatorImpl implements FunctionName {
         return names;
         
     }
-    
-    /**
-     * Validates the structure of arguments, basically enforcing java conventions for variable 
-     * level arguments.
-     */
-    private void validate() {
-        for (int i = 0; i < args.size(); i++) {
-            Parameter<?> arg = args.get(i);
-            if (arg.getMaxOccurs() == 0) {
-                throw new IllegalArgumentException(String.format("Argument %s has zero max"));
-            }
-            if (arg.getMinOccurs() != 1 || arg.getMaxOccurs() != 1) {
-                //this can only happen for the last argument
-                if (i != args.size()-1) {
-                    throw new IllegalArgumentException(String.format("Argument %s(%d,%d) invalid." +
-                        " Variable arguments must be the last argument of function.", 
-                    arg.getName(), arg.getMinOccurs(), arg.getMaxOccurs()));
-                }
-            }
-        }
-    }
 
     private static Parameter<?> generateReturn() {
         return parameter("return", Object.class);
diff --git a/modules/library/main/src/main/java/org/geotools/filter/function/string/StringInFunction.java b/modules/library/main/src/main/java/org/geotools/filter/function/string/StringInFunction.java
index fd127f2..f3a5a6c 100644
--- a/modules/library/main/src/main/java/org/geotools/filter/function/string/StringInFunction.java
+++ b/modules/library/main/src/main/java/org/geotools/filter/function/string/StringInFunction.java
@@ -35,7 +35,7 @@ public class StringInFunction extends FunctionImpl {
 
     @Override
     public Object evaluate(Object object) {
-        LinkedHashMap<String, Object> args = prepArguments(object);
+        LinkedHashMap<String, Object> args = dispatchArguments(object);
         
         String str = (String) args.get("string");
         Boolean matchCase = (Boolean) args.get("matchCase");