diff --git a/fe/src/main/java/org/apache/doris/planner/StreamLoadScanNode.java b/fe/src/main/java/org/apache/doris/planner/StreamLoadScanNode.java
index 8d0a4c2a78fda0..e17a3fc0b52ae9 100644
--- a/fe/src/main/java/org/apache/doris/planner/StreamLoadScanNode.java
+++ b/fe/src/main/java/org/apache/doris/planner/StreamLoadScanNode.java
@@ -329,9 +329,11 @@ private void finalizeParams() throws UserException {
     }
 
     private Expr castToSlot(SlotDescriptor slotDesc, Expr expr) throws UserException {
+        if (slotDesc.getType().isNull()) {
+            return expr;
+        }
         PrimitiveType dstType = slotDesc.getType().getPrimitiveType();
         PrimitiveType srcType = expr.getType().getPrimitiveType();
-
         if (dstType.isStringType()) {
             if (srcType.isStringType()) {
                 return expr;