diff --git a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/cbo/EnumerateJoinsRule.java b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/cbo/EnumerateJoinsRule.java
index c24dd7f..7ed23f7 100644
--- a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/cbo/EnumerateJoinsRule.java
+++ b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/cbo/EnumerateJoinsRule.java
@@ -1015,7 +1015,6 @@
     // on top of that LeafInput. Modify the joinLeafInputsHashMap as well.
     private void pushAssignsIntoLeafInputs(IPlanPrettyPrinter pp, List<ILogicalOperator> leafInputs,
             List<AssignOperator> assignOps, List<ILogicalExpression> assignJoinExprs) throws AlgebricksException {
-        int pos = 0;
         for (ILogicalOperator lo : leafInputs) {
             ILogicalOperator joinLeafInput = lo;
             printPlan(pp, (AbstractLogicalOperator) joinLeafInput, "Incoming leaf Input");
@@ -1023,10 +1022,8 @@
             if (assignNumber != -1) {
                 joinLeafInput = addAssignToLeafInput(joinLeafInput, assignOps.get(assignNumber));
                 printPlan(pp, (AbstractLogicalOperator) joinLeafInput, "Modified leaf Input");
-                leafInputs.add(pos, joinLeafInput);
                 assignOps.remove(assignNumber);
             }
-            pos++;
         }
     }
 
diff --git a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/cbo/JoinEnum.java b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/cbo/JoinEnum.java
index e748e55..76f87b2 100644
--- a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/cbo/JoinEnum.java
+++ b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/cbo/JoinEnum.java
@@ -440,6 +440,7 @@
             usedVars.clear();
             ILogicalExpression expr = jc.joinCondition;
             expr.getUsedVariables(usedVars);
+            List<AssignOperator> erase = new ArrayList<>();
             for (AssignOperator aOp : assignOps) {
                 for (int i = 0; i < aOp.getVariables().size(); i++) {
                     if (usedVars.contains(aOp.getVariables().get(i))) {
@@ -447,9 +448,13 @@
                                 aOp.getVariables().get(i), aOp.getExpressions().get(i).getValue());
                         jc.joinCondition = expr;
                         jc.selectivity = stats.getSelectivityFromAnnotationMain(jc.joinCondition, true);
+                        erase.add(aOp);
                     }
                 }
             }
+            for (int i = erase.size() - 1; i >= 0; i--) {
+                assignOps.remove(erase.get(i));
+            }
         }
 
         // now fill the datasetBits for each join condition.