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 edc3251..ee9ec4f 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
@@ -898,7 +898,7 @@
                 LimitOperator lop = (LimitOperator) op;
                 ILogicalExpression expr = lop.getMaxObjects().getValue();
                 if (expr != null) {
-                    if (expr.getExpressionTag() != LogicalExpressionTag.VARIABLE) { // must be a constant
+                    if (expr.getExpressionTag() == LogicalExpressionTag.CONSTANT) { // must be a constant
                         return Integer.parseInt(lop.getMaxObjects().getValue().toString());
                     }
                 }