diff --git a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/cbo/OperatorUtils.java b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/cbo/OperatorUtils.java
index f617a5a..f20e912 100644
--- a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/cbo/OperatorUtils.java
+++ b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/cbo/OperatorUtils.java
@@ -100,7 +100,7 @@
             }
 
             if (scanOp != null) {
-                ILogicalOperator inputOp = (selOp != null) ? selOp : ((assignOp != null) ? assignOp : scanOp);
+                ILogicalOperator inputOp = (assignOp != null) ? assignOp : ((selOp != null) ? selOp : scanOp);
                 SourceLocation sourceLocation = inputOp.getSourceLocation();
                 DistinctOperator distinctOp =
                         createDistinctOp(foundDistinctVars, inputOp, sourceLocation, distinctPair.second, context);
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/results_cbo/cardinality-estimation/join-queries/join-queries.3.plan b/asterixdb/asterix-app/src/test/resources/runtimets/results_cbo/cardinality-estimation/join-queries/join-queries.3.plan
index cd3f2d4..25d39e0 100644
--- a/asterixdb/asterix-app/src/test/resources/runtimets/results_cbo/cardinality-estimation/join-queries/join-queries.3.plan
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/results_cbo/cardinality-estimation/join-queries/join-queries.3.plan
@@ -1,8 +1,8 @@
-distribute result [$$35] [cardinality: 960.71, op-cost: 0.0, total-cost: 136471.34]
+distribute result [$$35] [cardinality: 924.07, op-cost: 0.0, total-cost: 136471.34]
 -- DISTRIBUTE_RESULT  |PARTITIONED|
-  exchange [cardinality: 960.71, op-cost: 0.0, total-cost: 136471.34]
+  exchange [cardinality: 924.07, op-cost: 0.0, total-cost: 136471.34]
   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-    distinct ([$$35]) [cardinality: 960.71, op-cost: 58474.7, total-cost: 136471.34]
+    distinct ([$$35]) [cardinality: 924.07, op-cost: 58474.7, total-cost: 136471.34]
     -- PRE_SORTED_DISTINCT_BY  |PARTITIONED|
       exchange [cardinality: 4783.64, op-cost: 0.0, total-cost: 77996.64]
       -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|