diff --git a/plugin/trino-iceberg/src/main/java/io/trino/plugin/iceberg/IcebergPageSourceProvider.java b/plugin/trino-iceberg/src/main/java/io/trino/plugin/iceberg/IcebergPageSourceProvider.java
index 439997b7885c..c2fd246ded1c 100644
--- a/plugin/trino-iceberg/src/main/java/io/trino/plugin/iceberg/IcebergPageSourceProvider.java
+++ b/plugin/trino-iceberg/src/main/java/io/trino/plugin/iceberg/IcebergPageSourceProvider.java
@@ -392,7 +392,8 @@ private static void populateMapping(
             fieldNameToIdMappingForTableColumns.put(
                     identity.getId(),
                     identity.getChildren().stream()
-                            .collect(toImmutableMap(ColumnIdentity::getName, ColumnIdentity::getId)));
+                            // Lower casing is required here because ORC StructColumnReader does the same before mapping
+                            .collect(toImmutableMap(child -> child.getName().toLowerCase(ENGLISH), ColumnIdentity::getId)));
 
             for (ColumnIdentity child : identity.getChildren()) {
                 populateMapping(child, fieldNameToIdMappingForTableColumns);
@@ -415,7 +416,9 @@ public IdBasedFieldMapper(Map<Integer, OrcColumn> idToColumnMappingForFile, Map<
         @Override
         public OrcColumn get(String fieldName)
         {
-            int fieldId = nameToIdMappingForTableColumns.get(fieldName);
+            int fieldId = requireNonNull(
+                    nameToIdMappingForTableColumns.get(fieldName),
+                    () -> format("Id mapping for field %s not found", fieldName));
             return idToColumnMappingForFile.get(fieldId);
         }
     }
diff --git a/testing/trino-product-tests-launcher/src/main/resources/docker/presto-product-tests/conf/environment/singlenode-spark-iceberg/iceberg.properties b/testing/trino-product-tests-launcher/src/main/resources/docker/presto-product-tests/conf/environment/singlenode-spark-iceberg/iceberg.properties
index 7ce5303954a3..c2cf659b1b1e 100644
--- a/testing/trino-product-tests-launcher/src/main/resources/docker/presto-product-tests/conf/environment/singlenode-spark-iceberg/iceberg.properties
+++ b/testing/trino-product-tests-launcher/src/main/resources/docker/presto-product-tests/conf/environment/singlenode-spark-iceberg/iceberg.properties
@@ -1,2 +1,4 @@
 connector.name=iceberg
 hive.metastore.uri=thrift://hadoop-master:9083
+# TODO: Remove this config to test default read behavior once Spark writer version is fixed. See https://github.com/trinodb/trino/issues/6369 for details
+iceberg.use-file-size-from-metadata=false
diff --git a/testing/trino-product-tests/src/main/java/io/trino/tests/iceberg/TestSparkCompatibility.java b/testing/trino-product-tests/src/main/java/io/trino/tests/iceberg/TestSparkCompatibility.java
index d5bd2f171212..a72056662515 100644
--- a/testing/trino-product-tests/src/main/java/io/trino/tests/iceberg/TestSparkCompatibility.java
+++ b/testing/trino-product-tests/src/main/java/io/trino/tests/iceberg/TestSparkCompatibility.java
@@ -367,11 +367,18 @@ public void testIdBasedFieldMapping()
         String prestoTableName = prestoTableName(baseTableName);
         String sparkTableName = sparkTableName(baseTableName);
 
-        onPresto().executeQuery(format(
-                "CREATE TABLE %s (_struct ROW(rename BIGINT, keep BIGINT, drop_and_add BIGINT), _partition BIGINT) "
-                        + "WITH (partitioning = ARRAY['_partition'])",
-                prestoTableName));
-        onPresto().executeQuery(format("INSERT INTO %s VALUES (row(1, 2, 3), 1001)", prestoTableName));
+        onSpark().executeQuery(format(
+                "CREATE TABLE %s (_struct STRUCT<rename:BIGINT, keep:BIGINT, drop_and_add:BIGINT, CaseSensitive:BIGINT>, _partition BIGINT)"
+                        + " USING ICEBERG"
+                        + " partitioned by (_partition)"
+                        + " TBLPROPERTIES ('write.format.default' = 'orc')",
+                sparkTableName));
+
+        onSpark().executeQuery(format(
+                "INSERT INTO TABLE %s SELECT "
+                        + "named_struct('rename', 1, 'keep', 2, 'drop_and_add', 3, 'CaseSensitive', 4), "
+                        + "1001",
+                sparkTableName));
 
         // Alter nested fields using Spark. Presto does not support this yet.
         onSpark().executeQuery(format("ALTER TABLE %s RENAME COLUMN _struct.rename TO renamed", sparkTableName));
@@ -383,6 +390,7 @@ public void testIdBasedFieldMapping()
                         // Rename does not change id
                         .addField("renamed", 1L)
                         .addField("keep", 2L)
+                        .addField("CaseSensitive", 4L)
                         // Dropping and re-adding changes id
                         .addField("drop_and_add", null)
                         .build(),