diff --git a/include/osg/VertexAttribDivisor b/include/osg/VertexAttribDivisor
index 7b222cd38..a38b31da5 100644
--- a/include/osg/VertexAttribDivisor
+++ b/include/osg/VertexAttribDivisor
@@ -50,6 +50,7 @@ class OSG_EXPORT VertexAttribDivisor : public StateAttribute
             COMPARE_StateAttribute_Types(VertexAttribDivisor,sa)
 
             // compare each parameter in turn against the rhs.
+            COMPARE_StateAttribute_Parameter(_index)
             COMPARE_StateAttribute_Parameter(_divisor)
 
             return 0; // passed all the above comparison macros, must be equal.