diff --git a/hyracks-algebricks/hyracks-algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/IsomorphismOperatorVisitor.java b/hyracks-algebricks/hyracks-algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/IsomorphismOperatorVisitor.java
index 31061db..b97597d 100644
--- a/hyracks-algebricks/hyracks-algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/IsomorphismOperatorVisitor.java
+++ b/hyracks-algebricks/hyracks-algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/IsomorphismOperatorVisitor.java
@@ -345,7 +345,7 @@
         AbstractLogicalOperator aop = (AbstractLogicalOperator) arg;
         if (aop.getOperatorTag() != LogicalOperatorTag.UNNEST_MAP)
             return Boolean.FALSE;
-        UnnestOperator unnestOpArg = (UnnestOperator) copyAndSubstituteVar(op, arg);
+        UnnestMapOperator unnestOpArg = (UnnestMapOperator) copyAndSubstituteVar(op, arg);
         boolean isomorphic = VariableUtilities.varListEqualUnordered(op.getVariables(), unnestOpArg.getVariables());
         if (!isomorphic)
             return Boolean.FALSE;