diff --git a/.travis.yml b/.travis.yml
index 19ea78a..0fa856f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -6,6 +6,7 @@ php:
   - 5.5
   - 5.6
   - 7.0
+  - 7.1
   - hhvm
 
 matrix:
diff --git a/composer.json b/composer.json
index 63adea9..5b2815a 100644
--- a/composer.json
+++ b/composer.json
@@ -16,8 +16,8 @@
 		}
 	},
 	"require": {
-		"php": ">=5.3.0",
-		"ext-mbstring": "*"
+		"symfony/polyfill-mbstring": "^1.3",
+		"php": ">=5.3.0"
 	},
 	"require-dev": {
 		"phpunit/phpunit": "~4.7",