Index: src/main/java/org/apache/maven/plugin/idea/IdeaProjectMojo.java
===================================================================
--- src/main/java/org/apache/maven/plugin/idea/IdeaProjectMojo.java	(revision 888559)
+++ src/main/java/org/apache/maven/plugin/idea/IdeaProjectMojo.java	(working copy)
@@ -66,6 +66,21 @@
     private String jdkLevel;
 
     /**
+     * Specify the language level to use for the features such as assert keywords (jdk 1.4)
+     * enums (jdk 1.5), or @Overrides for interface methods (jdk 1.6)
+     * Will only effect jdk 1.4+
+     * Literal values to use:
+     * <ul>
+     *  <li>JDK_1_4</li>
+     *  <li>JDK_1_5</li>
+     *  <li>JDK_1_6</li>
+     * </ul>
+     *
+     * @parameter expression="${jdkLanguageLevel}"
+     */
+    private String jdkLanguageLevel;
+
+    /**
      * Specify the resource pattern in wildcard format, for example "?*.xml;?*.properties".
      * Currently supports 4.x and 5.x.
      * Because IDEA doesn't distinguish between source and resources directories, this is needed.
@@ -237,20 +252,27 @@
         component.addAttribute( "project-jdk-name", jdkName );
 
         String jdkLevel = this.jdkLevel;
+
         if ( jdkLevel == null )
         {
             jdkLevel = System.getProperty( "java.specification.version" );
         }
 
+        String jdkLanguageLevel = this.jdkLanguageLevel;
+
         if ( jdkLevel.startsWith( "1.4" ) )
         {
             component.addAttribute( "assert-keyword", "true" );
             component.addAttribute( "jdk-15", "false" );
+
+            setLanguageLevel(component, jdkLevel, jdkLanguageLevel);
         }
         else if ( jdkLevel.compareTo( "1.5" ) >= 0 )
         {
             component.addAttribute( "assert-keyword", "true" );
             component.addAttribute( "jdk-15", "true" );
+
+            setLanguageLevel(component, jdkLevel, jdkLanguageLevel);
         }
         else
         {
@@ -258,6 +280,30 @@
         }
     }
 
+    private void setLanguageLevel(Element component, String jdkLevel, String jdkLanguageLevel)
+    {
+        getLog().info("jdkLanguageLevel = " + jdkLanguageLevel);
+
+        if(jdkLanguageLevel == null)
+        {
+            // could do this by parsing jdkLevel but I think idea is capped at 1_6
+            switch(jdkLevel.charAt(2))
+            {
+                case 4:
+                    jdkLanguageLevel = "JDK_1_4";
+                    break;
+                case 5:
+                    jdkLanguageLevel = "JDK_1_5";
+                    break;
+                default: // cap to 1_6
+                    jdkLanguageLevel = "JDK_1_6";
+                    break;
+            }
+        }
+
+        component.addAttribute("languageLevel", jdkLanguageLevel);        
+    }
+
     /**
      * Sets the wilcard resource patterns.
      *