diff --git a/classes/ComicPressTagBuilder.inc b/classes/ComicPressTagBuilder.inc
index 92238fd..861480b 100644
--- a/classes/ComicPressTagBuilder.inc
+++ b/classes/ComicPressTagBuilder.inc
@@ -104,7 +104,7 @@ class ComicPressTagBuilder {
 
 			if (in_array($state, array(self::HAS_POST_METHOD, self::HAS_EXTRACT_METHOD))) {
 				if ($current == "in") {
-					if (empty($parts)) {
+					if (implode('', $parts) == '') {
 						throw new ComicPressException("No category specified in tag ${method_name}");
 					}
 					$is_id = false;
@@ -120,7 +120,7 @@ class ComicPressTagBuilder {
 					break;
 				}
 
-				if (in_array($current, array('id', 'permalink', 'title', 'timestamp', 'date'))) {
+				if (in_array($current, array('id', 'permalink', 'title', 'timestamp', 'date', 'post'))) {
 					if ($state == self::HAS_EXTRACT_METHOD) {
 						throw new ComicPressException('Only one extract method can be specified');
 					}
diff --git a/test/ComicPressAdminTest.php b/test/ComicPressAdminTest.php
index 0ed9642..ef2aab0 100644
--- a/test/ComicPressAdminTest.php
+++ b/test/ComicPressAdminTest.php
@@ -129,7 +129,29 @@ class ComicPressAdminTest extends PHPUnit_Framework_TestCase {
     		array(
     			'enabled_backends' => array('ComicPressBackendURLFactory')
     		),
-    	)
+    	),
+    	array(
+    		array(
+    			'category_groupings' => array()
+    		),
+	    	array(
+	    		'category_groupings' => array(
+	    			'test' => array(
+	    				'name' => 'empty'
+	    			),
+	    			'test2' => array(
+	    				'name' => 'full',
+	    				'category' => array(1,2,3)
+	    			)
+	    		)
+	    	),
+	    	array(
+	    		'category_groupings' => array(
+	    			'full' => array(1,2,3),
+	    			'empty' => array()
+	    		)
+	    	)
+    	),
     );
   }
 
diff --git a/test/ComicPressTagBuilderTest.php b/test/ComicPressTagBuilderTest.php
index eb199ff..2a36999 100644
--- a/test/ComicPressTagBuilderTest.php
+++ b/test/ComicPressTagBuilderTest.php
@@ -213,6 +213,21 @@ class ComicPressTagBuilderTest extends PHPUnit_Framework_TestCase {
 		$this->assertEquals($expected_pieces, ComicPressTagBuilder::parse_method($method_name));
 	}
 
+	function providerTestMethodParserExceptions() {
+		return array(
+			array('first_in_'),
+			array('first_post_id')
+		);
+	}
+
+	/**
+	 * @dataProvider providerTestMethodParserExceptions
+	 * @expectedException ComicPressException
+	 */
+	function testMethodParserExceptions($method_name) {
+		ComicPressTagBuilder::parse_method($method_name);
+	}
+
 	function testMethodParserWithParam() {
 		extract($this->setupStorylineBuilderTest());