Index: Gruntfile.js
===================================================================
--- Gruntfile.js	(revision 45273)
+++ Gruntfile.js	(working copy)
@@ -110,6 +110,7 @@
 				WORKING_DIR + 'wp-admin/css/*rtl*',
 				WORKING_DIR + 'wp-includes/css/*.min.css',
 				WORKING_DIR + 'wp-includes/css/*rtl*',
+				WORKING_DIR + 'wp-includes/css/dist',
 				WORKING_DIR + 'wp-admin/css/colors/**/*.css'
 			],
 			js: [
@@ -501,6 +502,13 @@
 					'wp-admin/css/*.css',
 					'wp-includes/css/*.css',
 
+					// Exclude minified and already processed files.
+					// These are present when running `grunt build` after `grunt --dev`.
+					'!wp-admin/css/*-rtl.css',
+					'!wp-includes/css/*-rtl.css',
+					'!wp-admin/css/*.min.css',
+					'!wp-includes/css/*.min.css',
+
 					// Exceptions
 					'!wp-includes/css/dashicons.css',
 					'!wp-includes/css/wp-embed-template.css',
Index: src/wp-includes/css
===================================================================
--- src/wp-includes/css	(revision 45273)
+++ src/wp-includes/css	(working copy)

Property changes on: src/wp-includes/css
___________________________________________________________________
Modified: svn:ignore
## -1,3 +1,3 ##
 dist
 *.min.css
-
+*-rtl.css