diff --git a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/codeGen/SchemaProcessorImpl.kt b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/codeGen/SchemaProcessorImpl.kt
index 9517fbe078..31e25fb384 100644
--- a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/codeGen/SchemaProcessorImpl.kt
+++ b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/codeGen/SchemaProcessorImpl.kt
@@ -58,6 +58,7 @@ internal class SchemaProcessorImpl(
     private fun generateFields(
         schema: DataFrameSchema,
         visibility: MarkerVisibility,
+        openNestedDataSchemas: Boolean,
         requiredSuperMarkers: List<Marker> = emptyList(),
     ): List<GeneratedField> {
         val usedFieldNames =
@@ -66,18 +67,26 @@ internal class SchemaProcessorImpl(
         fun getFieldType(columnSchema: ColumnSchema): FieldType =
             when (columnSchema) {
                 is ColumnSchema.Value ->
-                    FieldType.ValueFieldType(columnSchema.type.toString())
+                    FieldType.ValueFieldType(typeFqName = columnSchema.type.toString())
 
                 is ColumnSchema.Group ->
                     FieldType.GroupFieldType(
-                        process(columnSchema.schema, false, visibility).name,
+                        markerName = process(
+                            schema = columnSchema.schema,
+                            isOpen = openNestedDataSchemas,
+                            visibility = visibility,
+                        ).name,
                         renderAsObject = true,
                     )
 
                 is ColumnSchema.Frame ->
                     FieldType.FrameFieldType(
-                        process(columnSchema.schema, false, visibility).name,
-                        columnSchema.nullable,
+                        markerName = process(
+                            schema = columnSchema.schema,
+                            isOpen = openNestedDataSchemas,
+                            visibility = visibility,
+                        ).name,
+                        nullable = columnSchema.nullable,
                         renderAsList = true,
                     )
 
@@ -145,11 +154,24 @@ internal class SchemaProcessorImpl(
                     }
                 }
             }
-            generateFields(scheme, visibility, baseMarkers)
+            generateFields(
+                schema = scheme,
+                visibility = visibility,
+                openNestedDataSchemas = isOpen,
+                requiredSuperMarkers = baseMarkers,
+            )
         } else {
-            generateFields(scheme, visibility)
+            generateFields(schema = scheme, visibility = visibility, openNestedDataSchemas = isOpen)
         }
-        return Marker(name, isOpen, fields, baseMarkers.onlyLeafs(), visibility, emptyList(), emptyList())
+        return Marker(
+            name = name,
+            isOpen = isOpen,
+            fields = fields,
+            superMarkers = baseMarkers.onlyLeafs(),
+            visibility = visibility,
+            typeParameters = emptyList(),
+            typeArguments = emptyList(),
+        )
     }
 
     private fun DataFrameSchema.getRequiredMarkers() = registeredMarkers.filterRequiredForSchema(this)
diff --git a/core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/CodeGenerationTests.kt b/core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/CodeGenerationTests.kt
index 1cfe07482d..3596948041 100644
--- a/core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/CodeGenerationTests.kt
+++ b/core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/CodeGenerationTests.kt
@@ -158,7 +158,7 @@ class CodeGenerationTests : BaseTest() {
         val type2 = ReplCodeGeneratorImpl.markerInterfacePrefix
         val declaration1 =
             """
-            @DataSchema(isOpen = false)
+            @DataSchema
             interface $type1 {
                 val city: String?
                 val name: String
diff --git a/core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/ReplCodeGenTests.kt b/core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/ReplCodeGenTests.kt
index 48f0c2e101..e762ee268e 100644
--- a/core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/ReplCodeGenTests.kt
+++ b/core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/ReplCodeGenTests.kt
@@ -277,7 +277,7 @@ class ReplCodeGenTests : BaseTest() {
         val c = repl.process(Test5.df, Test5::df)
         c.declarations shouldBe
             """
-            @DataSchema(isOpen = false)
+            @DataSchema
             interface _DataFrameType3 {
                 val a: Int
                 val c: Int
diff --git a/dataframe-jupyter/src/test/kotlin/org/jetbrains/kotlinx/dataframe/jupyter/CodeGenerationTests.kt b/dataframe-jupyter/src/test/kotlin/org/jetbrains/kotlinx/dataframe/jupyter/CodeGenerationTests.kt
index cdd2c1e318..1ad40fe1af 100644
--- a/dataframe-jupyter/src/test/kotlin/org/jetbrains/kotlinx/dataframe/jupyter/CodeGenerationTests.kt
+++ b/dataframe-jupyter/src/test/kotlin/org/jetbrains/kotlinx/dataframe/jupyter/CodeGenerationTests.kt
@@ -70,4 +70,27 @@ class CodeGenerationTests : DataFrameJupyterTest() {
         df1.leaf.c
         """.checkCompilation()
     }
+
+    // https://github.com/Kotlin/dataframe/issues/1222
+    @Test
+    fun `reusing marker with nullable column`() {
+        @Language("kt")
+        val _1 = """
+            val df1 = dataFrameOf("group" to columnOf("a" to columnOf(1, null, 3)))
+            val df2 = dataFrameOf("group" to columnOf("a" to columnOf(1, 2, 3)))
+            df1.group.a
+            df2.group.a
+            """.checkCompilation()
+    }
+
+    @Test
+    fun `not reusing marker with non-nullable column`() {
+        @Language("kt")
+        val _1 = """
+            val df1 = dataFrameOf("group" to columnOf("a" to columnOf(1, 2, 3)))
+            val df2 = dataFrameOf("group" to columnOf("a" to columnOf(1, null, 3)))
+            df1.group.a
+            df2.group.a
+            """.checkCompilation()
+    }
 }