comment fix
diff --git a/src/main/java/org/cloudera/htrace/Span.java b/src/main/java/org/cloudera/htrace/Span.java
index 02d433d..a489d98 100644
--- a/src/main/java/org/cloudera/htrace/Span.java
+++ b/src/main/java/org/cloudera/htrace/Span.java
@@ -57,7 +57,7 @@
   /** A pseudo-unique (random) number assigned to this span instance */
   long getSpanId();
 
-  /** The parent span: returns null if this is the root span */
+  /** The parent span: returns the NullSpan if this is the root span */
   Span getParent();
 
   /**