diff --git a/plugin/trino-exchange/src/main/java/io/trino/plugin/exchange/FileSystemExchangeSink.java b/plugin/trino-exchange/src/main/java/io/trino/plugin/exchange/FileSystemExchangeSink.java
index d1cad117b24a..c344bb2416d9 100644
--- a/plugin/trino-exchange/src/main/java/io/trino/plugin/exchange/FileSystemExchangeSink.java
+++ b/plugin/trino-exchange/src/main/java/io/trino/plugin/exchange/FileSystemExchangeSink.java
@@ -259,7 +259,7 @@ private void writeInternal(Slice slice)
         private void flushIfNeeded(boolean finished)
         {
             SliceOutput buffer = currentBuffer;
-            if (!buffer.isWritable() || finished) {
+            if (buffer != null && (!buffer.isWritable() || finished)) {
                 if (!buffer.isWritable()) {
                     currentBuffer = null;
                 }