diff --git a/framework/src/play/classloading/ApplicationClassloader.java b/framework/src/play/classloading/ApplicationClassloader.java
index 85d305f443..035d645a2a 100644
--- a/framework/src/play/classloading/ApplicationClassloader.java
+++ b/framework/src/play/classloading/ApplicationClassloader.java
@@ -26,6 +26,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 
 import org.apache.commons.io.IOUtils;
 import org.apache.commons.lang.StringUtils;
@@ -491,7 +492,7 @@ public List<Class> getAssignableClasses(Class clazz) {
     }
 
     // assignable classes cache
-    private final Map<String, List<Class>> assignableClassesByName = new HashMap<>(100);
+    private final Map<String, List<Class>> assignableClassesByName = new ConcurrentHashMap<>(100);
 
     /**
      * Find a class in a case insensitive way