diff --git wp-includes/class-wp-user.php wp-includes/class-wp-user.php
index 210919d..d0069c2 100644
--- wp-includes/class-wp-user.php
+++ wp-includes/class-wp-user.php
@@ -482,11 +482,15 @@ class WP_User {
 		if ( is_array( $this->caps ) )
 			$this->roles = array_filter( array_keys( $this->caps ), array( $wp_roles, 'is_role' ) );
 
-		//Build $allcaps from role caps, overlay user's $caps
+		/**
+		 * Build $allcaps from role caps, overlaying user's $caps and caps from
+		 * the user's roles. Role capabilities are filtered to only return caps
+		 * which are true. This prevents false caps overwriting true caps.
+		 */
 		$this->allcaps = array();
 		foreach ( (array) $this->roles as $role ) {
 			$the_role = $wp_roles->get_role( $role );
-			$this->allcaps = array_merge( (array) $this->allcaps, (array) $the_role->capabilities );
+			$this->allcaps = array_merge( (array) $this->allcaps, array_filter( (array) $the_role->capabilities ) );
 		}
 		$this->allcaps = array_merge( (array) $this->allcaps, (array) $this->caps );