diff --git a/.travis.yml b/.travis.yml
index a6e78dd8..76d10dd9 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -5,6 +5,8 @@ php:
   - 5.4
   - 5.5
   - 5.6
+  - 7.0
+  - 7.1
   - hhvm
 
 sudo: false
diff --git a/composer.json b/composer.json
index a2447af3..30708673 100644
--- a/composer.json
+++ b/composer.json
@@ -24,7 +24,7 @@
         }
     },
     "require-dev": {
-        "phpunit/phpunit": "~4.3"
+        "phpunit/phpunit": "^4 || ^5"
     },
     "scripts": {
         "test": "phpunit"
diff --git a/lessc.inc.php b/lessc.inc.php
index 2292f219..b639c3e2 100644
--- a/lessc.inc.php
+++ b/lessc.inc.php
@@ -1273,7 +1273,7 @@ protected function lib_contrast($args) {
 
 	protected function lib_luma($color) {
 	    $color = $this->coerceColor($color);
-	    return (0.2126 * $color[0] / 255) + (0.7152 * $color[1] / 255) + (0.0722 * $color[2] / 255);
+	    return (0.2126 * $color[1] / 255) + (0.7152 * $color[2] / 255) + (0.0722 * $color[3] / 255);
 	}