diff --git a/src/main/java/de/ids_mannheim/korap/query/serialize/PoliqarpPlusTree.java b/src/main/java/de/ids_mannheim/korap/query/serialize/PoliqarpPlusTree.java
index 2302fe3..2d650a9 100644
--- a/src/main/java/de/ids_mannheim/korap/query/serialize/PoliqarpPlusTree.java
+++ b/src/main/java/de/ids_mannheim/korap/query/serialize/PoliqarpPlusTree.java
@@ -520,7 +520,7 @@
 			if (negField) {
 				relation = relation.equals("or") ? "and": "or";
 			}
-			group.put("relation", relation);
+			group.put("relation", "relation:" + relation);
 			ArrayList<Object> groupOperands = new ArrayList<Object>();
 			group.put("operands", groupOperands);
 			fieldStack.push(groupOperands);
@@ -1009,4 +1009,4 @@
 		}
 	}
 
-}
\ No newline at end of file
+}