diff --git a/composer.json b/composer.json
index 2fcbb7f..5d50a99 100644
--- a/composer.json
+++ b/composer.json
@@ -11,7 +11,7 @@
         "bin-dir": "bin"
     },
     "require": {
-        "symfony/serializer": "^4.0",
+        "symfony/serializer": "3.4.15",
         "justinrainbow/json-schema": "5.2.7"
     }
 }
diff --git a/open_data_schema_map.make b/open_data_schema_map.make
index 43ec630..092cb6d 100644
--- a/open_data_schema_map.make
+++ b/open_data_schema_map.make
@@ -4,7 +4,7 @@ api = 2
 libraries[symfonyserializer][type] = libraries
 libraries[symfonyserializer][download][type] = "git"
 libraries[symfonyserializer][download][url] = "https://github.com/symfony/serializer.git"
-libraries[symfonyserializer][download][tag] = v3.4.2
+libraries[symfonyserializer][download][tag] = v3.4.15
 
 libraries[json-schema][type] = libraries
 libraries[json-schema][download][type] = "git"