--- a/net/minecraft/util/SharedConstants.java
+++ b/net/minecraft/util/SharedConstants.java
@@ -40,6 +40,7 @@
    }
 
    static {
+      if (System.getProperty("io.netty.leakDetection.level") == null) // Forge: allow level to be manually specified
       ResourceLeakDetector.setLevel(field_184877_a);
       CommandSyntaxException.ENABLE_COMMAND_STACK_TRACES = false;
       CommandSyntaxException.BUILT_IN_EXCEPTIONS = new TranslatableExceptionProvider();