Index: wp-admin/includes/media.php
===================================================================
--- wp-admin/includes/media.php	(revision 22704)
+++ wp-admin/includes/media.php	(working copy)
@@ -2280,13 +2280,14 @@
 			<label for="attachment_caption"><strong><?php _e( 'Caption' ); ?></strong></label><br />
 			<textarea class="widefat" name="excerpt" id="attachment_caption"><?php echo $post->post_excerpt; ?></textarea>
 		</p>
+<?php if ( substr( $post->post_mime_type, 0, 5 ) == 'image' ) : ?>
 		<p>
 			<label for="attachment_alt"><strong><?php _e( 'Alternative Text' ); ?></strong></label><br />
 			<input type="text" class="widefat" name="_wp_attachment_image_alt" id="attachment_alt" value="<?php echo esc_attr( $alt_text ); ?>" />
 		</p>
 	</div>
-	<?php
-	// need a filter on this content
+<?php
+	endif;
 }
 
 /**