diff --git a/Tests/Fixtures/yaml/services2.yml b/Tests/Fixtures/yaml/services2.yml
index 91de818f2..7ab302bcb 100644
--- a/Tests/Fixtures/yaml/services2.yml
+++ b/Tests/Fixtures/yaml/services2.yml
@@ -5,7 +5,7 @@ parameters:
         - false
         - 0
         - 1000.3
-        - !php/const:PHP_INT_MAX
+        - !php/const PHP_INT_MAX
     bar: foo
     escape: '@@escapeme'
     foo_bar: '@foo_bar'
diff --git a/composer.json b/composer.json
index 8135aae6b..2ca4cd048 100644
--- a/composer.json
+++ b/composer.json
@@ -20,7 +20,7 @@
         "psr/container": "^1.0"
     },
     "require-dev": {
-        "symfony/yaml": "~3.3|~4.0",
+        "symfony/yaml": "~3.4|~4.0",
         "symfony/config": "~3.3|~4.0",
         "symfony/expression-language": "~2.8|~3.0|~4.0"
     },
@@ -35,7 +35,7 @@
         "symfony/config": "<3.3.1",
         "symfony/finder": "<3.3",
         "symfony/proxy-manager-bridge": "<3.4",
-        "symfony/yaml": "<3.3"
+        "symfony/yaml": "<3.4"
     },
     "provide": {
         "psr/container-implementation": "1.0"