diff --git a/src/main/java/com/beust/jcommander/JCommander.java b/src/main/java/com/beust/jcommander/JCommander.java
index 59073c60..42632ff9 100644
--- a/src/main/java/com/beust/jcommander/JCommander.java
+++ b/src/main/java/com/beust/jcommander/JCommander.java
@@ -355,11 +355,26 @@ private void validateOptions() {
         }
 
         if (mainParameterDescription != null) {
+            // Make sure we have a main parameter if it was required
             if (mainParameterDescription.getParameter().required() &&
                     !mainParameterDescription.isAssigned()) {
                 throw new ParameterException("Main parameters are required (\""
                         + mainParameterDescription.getDescription() + "\")");
             }
+
+            // If the main parameter has an arity, make sure the correct number of parameters was passed
+            int arity = mainParameterDescription.getParameter().arity();
+            if (arity != Parameter.DEFAULT_ARITY) {
+                Object value = mainParameterDescription.getParameterized().get(mainParameterObject);
+                if (List.class.isAssignableFrom(value.getClass())) {
+                    int size = ((List<?>) value).size();
+                    if (size != arity) {
+                        throw new ParameterException("There should be exactly " + arity + " main parameters but "
+                                + size + " were found");
+                    }
+                }
+
+            }
         }
     }
 
diff --git a/src/main/java/com/beust/jcommander/Parameter.java b/src/main/java/com/beust/jcommander/Parameter.java
index 2fc00c5c..5944d92f 100644
--- a/src/main/java/com/beust/jcommander/Parameter.java
+++ b/src/main/java/com/beust/jcommander/Parameter.java
@@ -60,7 +60,8 @@
    * How many parameter values this parameter will consume. For example,
    * an arity of 2 will allow "-pair value1 value2".
    */
-  int arity() default -1;
+  public static int DEFAULT_ARITY = -1;
+  int arity() default DEFAULT_ARITY;
 
   /**
    * If true, this parameter is a password and it will be prompted on the console
diff --git a/src/test/java/com/beust/jcommander/JCommanderTest.java b/src/test/java/com/beust/jcommander/JCommanderTest.java
index e967ef7b..1b981763 100644
--- a/src/test/java/com/beust/jcommander/JCommanderTest.java
+++ b/src/test/java/com/beust/jcommander/JCommanderTest.java
@@ -33,6 +33,9 @@
 import java.io.*;
 import java.math.BigDecimal;
 import java.nio.charset.Charset;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
 import java.text.ParseException;
 import java.text.SimpleDateFormat;
 import java.util.*;
@@ -1518,16 +1521,58 @@ class Args {
         Assert.assertEquals(args.f, false);
     }
 
+    @Test
+    public void mainParameterWithCorrectArity() {
+        class Args {
+            @Parameter(arity = 2)
+            private List<String> main;
+        }
+
+        Args args = new Args();
+        JCommander.newBuilder()
+                .addObject(args)
+                .args(new String[]{"a", "b"})
+                .build();
+        Assert.assertEquals(args.main.size(), 2);
+        Assert.assertEquals(args.main.get(0), "a");
+        Assert.assertEquals(args.main.get(1), "b");
+    }
+
+    @Test(expectedExceptions = ParameterException.class)
+    public void mainParameterWithWrongArity() {
+        class Args {
+            @Parameter(arity = 2)
+            private List<String> main;
+        }
+
+        Args args = new Args();
+        JCommander.newBuilder()
+                .addObject(args)
+                .args(new String[]{"a"})
+                .build();
+    }
+
     @Test(enabled = false)
     public static void main(String[] args) {
 
-        CommandTemplate template = new CommandTemplate();
-        JCommander jcommander = new JCommander(template);
-        jcommander.setProgramName("prog");
-        jcommander.parse("help");
+        class FileValidator implements IParameterValidator {
+            @Override
+            public void validate(String name, String value) throws ParameterException {
+                if (!Files.exists(Paths.get(value))) {
+                    throw new ParameterException("FILE_DOES_NOT_EXIST");
+                }
+            }
+        }
 
-        if (template.help) {
-            jcommander.usage();
+        class Args {
+            @Parameter(names = "--file", validateWith = FileValidator.class, required = true,
+                    description = "The properties file containing setup information.")
+            private Path propertiesFile = Paths.get("");
         }
+
+        JCommander.newBuilder()
+                    .addObject(new Args())
+                    .build()
+                    .parse("--file", "README.markdown");
     }
 }