diff --git a/spark/src/main/java/org/apache/iceberg/spark/source/RowDataRewriter.java b/spark/src/main/java/org/apache/iceberg/spark/source/RowDataRewriter.java
index 06793c5b01a9..07c7e008bab6 100644
--- a/spark/src/main/java/org/apache/iceberg/spark/source/RowDataRewriter.java
+++ b/spark/src/main/java/org/apache/iceberg/spark/source/RowDataRewriter.java
@@ -104,7 +104,7 @@ private List<DataFile> rewriteDataForTask(CombinedScanTask task) throws Exceptio
         spec, format, locations, io.value(), encryptionManager.value(), partitionId, taskId);
 
     TaskWriter<InternalRow> writer;
-    if (spec.fields().isEmpty()) {
+    if (spec.isUnpartitioned()) {
       writer = new UnpartitionedWriter<>(spec, format, appenderFactory, fileFactory, io.value(),
           Long.MAX_VALUE);
     } else if (PropertyUtil.propertyAsBoolean(properties,
diff --git a/spark2/src/main/java/org/apache/iceberg/spark/source/Writer.java b/spark2/src/main/java/org/apache/iceberg/spark/source/Writer.java
index 51ec5956f862..f54eae796e6b 100644
--- a/spark2/src/main/java/org/apache/iceberg/spark/source/Writer.java
+++ b/spark2/src/main/java/org/apache/iceberg/spark/source/Writer.java
@@ -278,7 +278,7 @@ public DataWriter<InternalRow> createDataWriter(int partitionId, long taskId, lo
           spec, format, locations, io.value(), encryptionManager.value(), partitionId, taskId);
       SparkAppenderFactory appenderFactory = new SparkAppenderFactory(properties, writeSchema, dsSchema, spec);
 
-      if (spec.fields().isEmpty()) {
+      if (spec.isUnpartitioned()) {
         return new Unpartitioned24Writer(spec, format, appenderFactory, fileFactory, io.value(), targetFileSize);
       } else if (partitionedFanoutEnabled) {
         return new PartitionedFanout24Writer(spec, format, appenderFactory, fileFactory, io.value(), targetFileSize,
diff --git a/spark3/src/main/java/org/apache/iceberg/spark/source/SparkWrite.java b/spark3/src/main/java/org/apache/iceberg/spark/source/SparkWrite.java
index c5c3faade41a..2fc803f8b090 100644
--- a/spark3/src/main/java/org/apache/iceberg/spark/source/SparkWrite.java
+++ b/spark3/src/main/java/org/apache/iceberg/spark/source/SparkWrite.java
@@ -516,7 +516,7 @@ public DataWriter<InternalRow> createWriter(int partitionId, long taskId, long e
       OutputFileFactory fileFactory = new OutputFileFactory(
           spec, format, locations, io.value(), encryptionManager.value(), partitionId, taskId);
       SparkAppenderFactory appenderFactory = new SparkAppenderFactory(properties, writeSchema, dsSchema, spec);
-      if (spec.fields().isEmpty()) {
+      if (spec.isUnpartitioned()) {
         return new Unpartitioned3Writer(spec, format, appenderFactory, fileFactory, io.value(), targetFileSize);
       } else if (partitionedFanoutEnabled) {
         return new PartitionedFanout3Writer(