diff --git a/modules/concurrent/src/main/java/org/terrier/structures/concurrent/ConcurrentDocumentIndex.java b/modules/concurrent/src/main/java/org/terrier/structures/concurrent/ConcurrentDocumentIndex.java
index b4511c09..0f81dc57 100644
--- a/modules/concurrent/src/main/java/org/terrier/structures/concurrent/ConcurrentDocumentIndex.java
+++ b/modules/concurrent/src/main/java/org/terrier/structures/concurrent/ConcurrentDocumentIndex.java
@@ -47,9 +47,8 @@ public DocumentIndexEntry getDocumentEntry(int docid) throws IOException {
 	}
 
 	public int getDocumentLength(int docid) throws IOException {
-		synchronized (parent) {
-			return parent.getDocumentLength(docid);
-		}		
+		// we dont synchronize on getDocumentLength() - we assume this is always in memory and reentrant
+		return parent.getDocumentLength(docid);	
 	}
 
 	public int getNumberOfDocuments() {