diff --git a/spark/src/main/scala/org/apache/spark/sql/comet/CometScanExec.scala b/spark/src/main/scala/org/apache/spark/sql/comet/CometScanExec.scala
index 7b6ab9d6a..eb9d5cb31 100644
--- a/spark/src/main/scala/org/apache/spark/sql/comet/CometScanExec.scala
+++ b/spark/src/main/scala/org/apache/spark/sql/comet/CometScanExec.scala
@@ -505,6 +505,8 @@ object CometScanExec extends DataTypeSupport {
   }
 
   def isFileFormatSupported(fileFormat: FileFormat): Boolean = {
+    // Only support Spark's built-in Parquet scans, not others such as Delta which use a subclass
+    // of ParquetFileFormat.
     fileFormat.getClass().equals(classOf[ParquetFileFormat])
   }
 }