diff --git a/wp-admin/admin-functions.php b/wp-admin/admin-functions.php
index d9cb58f66..a0ecbb825 100644
--- a/wp-admin/admin-functions.php
+++ b/wp-admin/admin-functions.php
@@ -1664,45 +1664,6 @@ function wp_handle_upload_error(&$file, $message) {
 		__("Missing a temporary folder."),
 		__("Failed to write file to disk."));
 
-	// Accepted MIME types are set here as PCRE. Override with $override['mimes'].
-	$mimes = apply_filters('upload_mimes', array (
-		'jpg|jpeg|jpe' => 'image/jpeg',
-		'gif' => 'image/gif',
-		'png' => 'image/png',
-		'bmp' => 'image/bmp',
-		'tif|tiff' => 'image/tiff',
-		'ico' => 'image/x-icon',
-		'asf|asx|wax|wmv|wmx' => 'video/asf',
-		'avi' => 'video/avi',
-		'mov|qt' => 'video/quicktime',
-		'mpeg|mpg|mpe' => 'video/mpeg',
-		'txt|c|cc|h' => 'text/plain',
-		'rtx' => 'text/richtext',
-		'css' => 'text/css',
-		'htm|html' => 'text/html',
-		'mp3|mp4' => 'audio/mpeg',
-		'ra|ram' => 'audio/x-realaudio',
-		'wav' => 'audio/wav',
-		'ogg' => 'audio/ogg',
-		'mid|midi' => 'audio/midi',
-		'wma' => 'audio/wma',
-		'rtf' => 'application/rtf',
-		'js' => 'application/javascript',
-		'pdf' => 'application/pdf',
-		'doc' => 'application/msword',
-		'pot|pps|ppt' => 'application/vnd.ms-powerpoint',
-		'wri' => 'application/vnd.ms-write',
-		'xla|xls|xlt|xlw' => 'application/vnd.ms-excel',
-		'mdb' => 'application/vnd.ms-access',
-		'mpp' => 'application/vnd.ms-project',
-		'swf' => 'application/x-shockwave-flash',
-		'class' => 'application/java',
-		'tar' => 'application/x-tar',
-		'zip' => 'application/zip',
-		'gz|gzip' => 'application/x-gzip',
-		'exe' => 'application/x-msdownload'
-	));
-
 	// All tests are on by default. Most can be turned off by $override[{test_name}] = false;
 	$test_form = true;
 	$test_size = true;
@@ -1730,17 +1691,11 @@ function wp_handle_upload_error(&$file, $message) {
 	if (! @ is_uploaded_file($file['tmp_name']) )
 		return $upload_error_handler($file, __('Specified file failed upload test.'));
 
-	// A correct MIME type will pass this test.
+	// A correct MIME type will pass this test. Override $mimes or use the upload_mimes filter.
 	if ( $test_type ) {
-		$type = false;
-		$ext = false;
-		foreach ($mimes as $ext_preg => $mime_match) {
-			$ext_preg = '![^.]\.(' . $ext_preg . ')$!i';
-			if ( preg_match($ext_preg, $file['name'], $ext_matches) ) {
-				$type = $mime_match;
-				$ext = $ext_matches[1];
-			}
-		}
+		$wp_filetype = wp_check_filetype($file['name'], $mimes);
+
+		extract($wp_filetype);
 
 		if ( !$type || !$ext )
 			return $upload_error_handler($file, __('File type does not meet security guidelines. Try another.'));
diff --git a/wp-includes/functions-post.php b/wp-includes/functions-post.php
index 8713779a7..fd9d8be5b 100644
--- a/wp-includes/functions-post.php
+++ b/wp-includes/functions-post.php
@@ -917,7 +917,11 @@ function wp_upload_dir() {
 
 function wp_upload_bits($name, $type, $bits) {
 	if ( empty($name) )
-		return array('error' => "Empty filename");
+		return array('error' => __("Empty filename"));
+
+	$wp_filetype = wp_check_filetype($name);
+	if ( !$wp_filetype['ext'] )
+		return array('error' => __("Invalid file type"));
 
 	$upload = wp_upload_dir();
 	
@@ -963,4 +967,59 @@ function wp_upload_bits($name, $type, $bits) {
 	return array('file' => $new_file, 'url' => $url, 'error' => false);
 }
 
+function wp_check_filetype($filename, $mimes = null) {
+	// Accepted MIME types are set here as PCRE unless provided.
+	$mimes = is_array($mimes) ? $mimes : apply_filters('upload_mimes', array (
+		'jpg|jpeg|jpe' => 'image/jpeg',
+		'gif' => 'image/gif',
+		'png' => 'image/png',
+		'bmp' => 'image/bmp',
+		'tif|tiff' => 'image/tiff',
+		'ico' => 'image/x-icon',
+		'asf|asx|wax|wmv|wmx' => 'video/asf',
+		'avi' => 'video/avi',
+		'mov|qt' => 'video/quicktime',
+		'mpeg|mpg|mpe' => 'video/mpeg',
+		'txt|c|cc|h' => 'text/plain',
+		'rtx' => 'text/richtext',
+		'css' => 'text/css',
+		'htm|html' => 'text/html',
+		'mp3|mp4' => 'audio/mpeg',
+		'ra|ram' => 'audio/x-realaudio',
+		'wav' => 'audio/wav',
+		'ogg' => 'audio/ogg',
+		'mid|midi' => 'audio/midi',
+		'wma' => 'audio/wma',
+		'rtf' => 'application/rtf',
+		'js' => 'application/javascript',
+		'pdf' => 'application/pdf',
+		'doc' => 'application/msword',
+		'pot|pps|ppt' => 'application/vnd.ms-powerpoint',
+		'wri' => 'application/vnd.ms-write',
+		'xla|xls|xlt|xlw' => 'application/vnd.ms-excel',
+		'mdb' => 'application/vnd.ms-access',
+		'mpp' => 'application/vnd.ms-project',
+		'swf' => 'application/x-shockwave-flash',
+		'class' => 'application/java',
+		'tar' => 'application/x-tar',
+		'zip' => 'application/zip',
+		'gz|gzip' => 'application/x-gzip',
+		'exe' => 'application/x-msdownload'
+	));
+
+	$type = false;
+	$ext = false;
+
+	foreach ($mimes as $ext_preg => $mime_match) {
+		$ext_preg = '!\.(' . $ext_preg . ')$!i';
+		if ( preg_match($ext_preg, $filename, $ext_matches) ) {
+			$type = $mime_match;
+			$ext = $ext_matches[1];
+			break;
+		}
+	}
+
+	return compact('ext', 'type');
+}
+
 ?>