diff --git a/src/main/java/uk/ac/ebi/utils/collections/OptionsMapWrapper.java b/src/main/java/uk/ac/ebi/utils/collections/OptionsMapWrapper.java
index 09f82bdbc..96e5369ff 100644
--- a/src/main/java/uk/ac/ebi/utils/collections/OptionsMapWrapper.java
+++ b/src/main/java/uk/ac/ebi/utils/collections/OptionsMapWrapper.java
@@ -169,7 +169,7 @@ public Object merge ( String key, Object value, BiFunction<? super Object, ? sup
 	@Override
 	public String toString ()
 	{
-		return this.getClass ().getSimpleName () + base.toString ();
+		return "[" + this.getClass ().getSimpleName () + "] " + base.toString ();
 	}
 	
 }