diff --git a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/IsomorphismOperatorVisitor.java b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/IsomorphismOperatorVisitor.java
index 31061db..b97597d 100644
--- a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/IsomorphismOperatorVisitor.java
+++ b/algebricks/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;
diff --git a/algebricks/algebricks-rewriter/src/main/java/edu/uci/ics/hyracks/algebricks/rewriter/rules/ExtractCommonExpressionsRule.java b/algebricks/algebricks-rewriter/src/main/java/edu/uci/ics/hyracks/algebricks/rewriter/rules/ExtractCommonExpressionsRule.java
index cbe2b4a..f017e0f 100644
--- a/algebricks/algebricks-rewriter/src/main/java/edu/uci/ics/hyracks/algebricks/rewriter/rules/ExtractCommonExpressionsRule.java
+++ b/algebricks/algebricks-rewriter/src/main/java/edu/uci/ics/hyracks/algebricks/rewriter/rules/ExtractCommonExpressionsRule.java
@@ -94,6 +94,8 @@
  */
 public class ExtractCommonExpressionsRule implements IAlgebraicRewriteRule {
 
+    private final List<ILogicalExpression> originalAssignExprs = new ArrayList<ILogicalExpression>();
+    
     private final CommonExpressionSubstitutionVisitor substVisitor = new CommonExpressionSubstitutionVisitor();
     private final Map<ILogicalExpression, ExprEquivalenceClass> exprEqClassMap = new HashMap<ILogicalExpression, ExprEquivalenceClass>();
     
@@ -124,11 +126,11 @@
         return modified;
     }
 
-    private void updateEquivalenceClassMap(LogicalVariable lhs, Mutable<ILogicalExpression> rhsExprRef, ILogicalOperator op) {
-        ExprEquivalenceClass exprEqClass = exprEqClassMap.get(rhsExprRef.getValue());
+    private void updateEquivalenceClassMap(LogicalVariable lhs, Mutable<ILogicalExpression> rhsExprRef, ILogicalExpression rhsExpr, ILogicalOperator op) {
+        ExprEquivalenceClass exprEqClass = exprEqClassMap.get(rhsExpr);
         if (exprEqClass == null) {
             exprEqClass = new ExprEquivalenceClass(op, rhsExprRef);
-            exprEqClassMap.put(rhsExprRef.getValue(), exprEqClass);
+            exprEqClassMap.put(rhsExpr, exprEqClass);
         }
         exprEqClass.setVariable(lhs);
     }
@@ -159,6 +161,19 @@
             return modified;
         }
         
+        // Remember a copy of the original assign expressions, so we can add them to the equivalence class map
+        // after replacing expressions within the assign operator itself.
+        if (op.getOperatorTag() == LogicalOperatorTag.ASSIGN) {
+            AssignOperator assignOp = (AssignOperator) op;
+            originalAssignExprs.clear();
+            int numVars = assignOp.getVariables().size();
+            for (int i = 0; i < numVars; i++) {
+                Mutable<ILogicalExpression> exprRef = assignOp.getExpressions().get(i);
+                ILogicalExpression expr = exprRef.getValue();
+                originalAssignExprs.add(expr.cloneExpression());
+            }
+        }
+        
         // Perform common subexpression elimination.
         substVisitor.setOperator(op);
         if (op.acceptExpressionTransform(substVisitor)) {
@@ -178,7 +193,10 @@
                 }
                 // Update equivalence class map.
                 LogicalVariable lhs = assignOp.getVariables().get(i);
-                updateEquivalenceClassMap(lhs, exprRef, op);
+                updateEquivalenceClassMap(lhs, exprRef, exprRef.getValue(), op);
+                
+                // Update equivalence class map with original assign expression.
+                updateEquivalenceClassMap(lhs, exprRef, originalAssignExprs.get(i), op);
             }
         }