diff --git a/Makefile b/Makefile
index b293581..54782b1 100644
--- a/Makefile
+++ b/Makefile
@@ -14,5 +14,8 @@ codegen-extensions:
 lint:
 	uvx ruff@0.11.11 check
 
+lint_fix:
+	uvx ruff@0.11.11 check --fix
+
 format:
 	uvx ruff@0.11.11 format
diff --git a/src/substrait/builders/plan.py b/src/substrait/builders/plan.py
index eca32da..ed487c7 100644
--- a/src/substrait/builders/plan.py
+++ b/src/substrait/builders/plan.py
@@ -34,6 +34,11 @@ def _merge_extensions(*objs):
 def read_named_table(
     names: Union[str, Iterable[str]], named_struct: stt.NamedStruct
 ) -> UnboundPlan:
+    if named_struct.struct.nullability is stt.Type.NULLABILITY_NULLABLE:
+        raise Exception("NamedStruct must not contain a nullable struct")
+    elif named_struct.struct.nullability is stt.Type.NULLABILITY_UNSPECIFIED:
+        named_struct.struct.nullability = stt.Type.NULLABILITY_REQUIRED
+
     def resolve(registry: ExtensionRegistry) -> stp.Plan:
         _names = [names] if isinstance(names, str) else names
 
diff --git a/src/substrait/builders/type.py b/src/substrait/builders/type.py
index 8405595..39ed5e6 100644
--- a/src/substrait/builders/type.py
+++ b/src/substrait/builders/type.py
@@ -257,4 +257,9 @@ def map(key: stt.Type, value: stt.Type, nullable=True) -> stt.Type:
 
 
 def named_struct(names: Iterable[str], struct: stt.Type) -> stt.NamedStruct:
+    if struct.struct.nullability is stt.Type.NULLABILITY_NULLABLE:
+        raise Exception("NamedStruct must not contain a nullable struct")
+    elif struct.struct.nullability is stt.Type.NULLABILITY_UNSPECIFIED:
+        struct.struct.nullability = stt.Type.NULLABILITY_REQUIRED
+
     return stt.NamedStruct(names=names, struct=struct.struct)
diff --git a/tests/builders/extended_expression/test_aggregate_function.py b/tests/builders/extended_expression/test_aggregate_function.py
index 8415df4..3211c0c 100644
--- a/tests/builders/extended_expression/test_aggregate_function.py
+++ b/tests/builders/extended_expression/test_aggregate_function.py
@@ -12,7 +12,8 @@
         stt.Type(i64=stt.Type.I64(nullability=stt.Type.NULLABILITY_REQUIRED)),
         stt.Type(string=stt.Type.String(nullability=stt.Type.NULLABILITY_NULLABLE)),
         stt.Type(fp32=stt.Type.FP32(nullability=stt.Type.NULLABILITY_NULLABLE)),
-    ]
+    ],
+    nullability=stt.Type.Nullability.NULLABILITY_REQUIRED,
 )
 
 named_struct = stt.NamedStruct(
diff --git a/tests/builders/extended_expression/test_scalar_function.py b/tests/builders/extended_expression/test_scalar_function.py
index 0f3e9e8..7c0bdeb 100644
--- a/tests/builders/extended_expression/test_scalar_function.py
+++ b/tests/builders/extended_expression/test_scalar_function.py
@@ -68,7 +68,7 @@ def test_sclar_add():
         extensions=[
             ste.SimpleExtensionDeclaration(
                 extension_function=ste.SimpleExtensionDeclaration.ExtensionFunction(
-                    extension_uri_reference=1, function_anchor=1, name="test_func:i8"   
+                    extension_uri_reference=1, function_anchor=1, name="test_func:i8"
                 )
             )
         ],
diff --git a/tests/builders/plan/test_aggregate.py b/tests/builders/plan/test_aggregate.py
index 9b36ad6..7b15c67 100644
--- a/tests/builders/plan/test_aggregate.py
+++ b/tests/builders/plan/test_aggregate.py
@@ -28,7 +28,9 @@
 registry = ExtensionRegistry(load_default_extensions=False)
 registry.register_extension_dict(yaml.safe_load(content), uri="test_uri")
 
-struct = stt.Type.Struct(types=[i64(nullable=False), boolean()])
+struct = stt.Type.Struct(
+    types=[i64(nullable=False), boolean()], nullability=stt.Type.NULLABILITY_REQUIRED
+)
 
 named_struct = stt.NamedStruct(names=["id", "is_applicable"], struct=struct)
 
diff --git a/tests/builders/plan/test_cross.py b/tests/builders/plan/test_cross.py
index 9a47ba4..e022706 100644
--- a/tests/builders/plan/test_cross.py
+++ b/tests/builders/plan/test_cross.py
@@ -7,13 +7,17 @@
 
 registry = ExtensionRegistry(load_default_extensions=False)
 
-struct = stt.Type.Struct(types=[i64(nullable=False), boolean()])
+struct = stt.Type.Struct(
+    types=[i64(nullable=False), boolean()], nullability=stt.Type.NULLABILITY_REQUIRED
+)
 
 named_struct = stt.NamedStruct(names=["id", "is_applicable"], struct=struct)
 
 named_struct_2 = stt.NamedStruct(
     names=["fk_id", "name"],
-    struct=stt.Type.Struct(types=[i64(nullable=False), string()]),
+    struct=stt.Type.Struct(
+        types=[i64(nullable=False), string()], nullability=stt.Type.NULLABILITY_REQUIRED
+    ),
 )
 
 
diff --git a/tests/builders/plan/test_fetch.py b/tests/builders/plan/test_fetch.py
index ebcd372..a9f8a4d 100644
--- a/tests/builders/plan/test_fetch.py
+++ b/tests/builders/plan/test_fetch.py
@@ -8,7 +8,9 @@
 
 registry = ExtensionRegistry(load_default_extensions=False)
 
-struct = stt.Type.Struct(types=[i64(nullable=False), boolean()])
+struct = stt.Type.Struct(
+    types=[i64(nullable=False), boolean()], nullability=stt.Type.NULLABILITY_REQUIRED
+)
 
 named_struct = stt.NamedStruct(names=["id", "is_applicable"], struct=struct)
 
diff --git a/tests/builders/plan/test_filter.py b/tests/builders/plan/test_filter.py
index 659f402..bba55ec 100644
--- a/tests/builders/plan/test_filter.py
+++ b/tests/builders/plan/test_filter.py
@@ -8,7 +8,9 @@
 
 registry = ExtensionRegistry(load_default_extensions=False)
 
-struct = stt.Type.Struct(types=[i64(nullable=False), boolean()])
+struct = stt.Type.Struct(
+    types=[i64(nullable=False), boolean()], nullability=stt.Type.NULLABILITY_REQUIRED
+)
 
 named_struct = stt.NamedStruct(names=["id", "is_applicable"], struct=struct)
 
diff --git a/tests/builders/plan/test_join.py b/tests/builders/plan/test_join.py
index 8d4998a..d6503cc 100644
--- a/tests/builders/plan/test_join.py
+++ b/tests/builders/plan/test_join.py
@@ -8,13 +8,17 @@
 
 registry = ExtensionRegistry(load_default_extensions=False)
 
-struct = stt.Type.Struct(types=[i64(nullable=False), boolean()])
+struct = stt.Type.Struct(
+    types=[i64(nullable=False), boolean()], nullability=stt.Type.NULLABILITY_REQUIRED
+)
 
 named_struct = stt.NamedStruct(names=["id", "is_applicable"], struct=struct)
 
 named_struct_2 = stt.NamedStruct(
     names=["fk_id", "name"],
-    struct=stt.Type.Struct(types=[i64(nullable=False), string()]),
+    struct=stt.Type.Struct(
+        types=[i64(nullable=False), string()], nullability=stt.Type.NULLABILITY_REQUIRED
+    ),
 )
 
 
diff --git a/tests/builders/plan/test_project.py b/tests/builders/plan/test_project.py
index 2dd9ff1..e66a499 100644
--- a/tests/builders/plan/test_project.py
+++ b/tests/builders/plan/test_project.py
@@ -8,7 +8,9 @@
 
 registry = ExtensionRegistry(load_default_extensions=False)
 
-struct = stt.Type.Struct(types=[i64(nullable=False), boolean()])
+struct = stt.Type.Struct(
+    types=[i64(nullable=False), boolean()], nullability=stt.Type.NULLABILITY_REQUIRED
+)
 
 named_struct = stt.NamedStruct(names=["id", "is_applicable"], struct=struct)
 
diff --git a/tests/builders/plan/test_read.py b/tests/builders/plan/test_read.py
index 6e380b8..909216a 100644
--- a/tests/builders/plan/test_read.py
+++ b/tests/builders/plan/test_read.py
@@ -3,8 +3,12 @@
 import substrait.gen.proto.algebra_pb2 as stalg
 from substrait.builders.type import boolean, i64
 from substrait.builders.plan import read_named_table
+import pytest
 
-struct = stt.Type.Struct(types=[i64(nullable=False), boolean()])
+struct = stt.Type.Struct(
+    types=[i64(nullable=False), boolean()],
+    nullability=stt.Type.Nullability.NULLABILITY_REQUIRED,
+)
 
 named_struct = stt.NamedStruct(names=["id", "is_applicable"], struct=struct)
 
@@ -57,3 +61,16 @@ def test_read_rel_db():
     )
 
     assert actual == expected
+
+
+def test_read_rel_schema_nullable():
+    struct = stt.Type.Struct(
+        types=[i64(nullable=False), boolean()],
+        nullability=stt.Type.Nullability.NULLABILITY_NULLABLE,
+    )
+
+    named_struct = stt.NamedStruct(names=["id", "is_applicable"], struct=struct)
+    with pytest.raises(
+        Exception, match=r"NamedStruct must not contain a nullable struct"
+    ):
+        read_named_table("example_table", named_struct)(None)
diff --git a/tests/builders/plan/test_set.py b/tests/builders/plan/test_set.py
index e761707..e35570d 100644
--- a/tests/builders/plan/test_set.py
+++ b/tests/builders/plan/test_set.py
@@ -7,7 +7,9 @@
 
 registry = ExtensionRegistry(load_default_extensions=False)
 
-struct = stt.Type.Struct(types=[i64(nullable=False), boolean()])
+struct = stt.Type.Struct(
+    types=[i64(nullable=False), boolean()], nullability=stt.Type.NULLABILITY_REQUIRED
+)
 
 named_struct = stt.NamedStruct(names=["id", "is_applicable"], struct=struct)
 
diff --git a/tests/builders/plan/test_sort.py b/tests/builders/plan/test_sort.py
index 4b4f49c..7fee44f 100644
--- a/tests/builders/plan/test_sort.py
+++ b/tests/builders/plan/test_sort.py
@@ -9,7 +9,9 @@
 
 registry = ExtensionRegistry(load_default_extensions=False)
 
-struct = stt.Type.Struct(types=[i64(nullable=False), boolean()])
+struct = stt.Type.Struct(
+    types=[i64(nullable=False), boolean()], nullability=stt.Type.NULLABILITY_REQUIRED
+)
 
 named_struct = stt.NamedStruct(names=["id", "is_applicable"], struct=struct)
 
diff --git a/tests/builders/test_types.py b/tests/builders/test_types.py
new file mode 100644
index 0000000..3d0e2d3
--- /dev/null
+++ b/tests/builders/test_types.py
@@ -0,0 +1,37 @@
+import substrait.gen.proto.type_pb2 as stt
+from substrait.builders.type import boolean, i64
+from substrait.builders.type import named_struct
+import pytest
+
+
+def test_named_struct_required():
+    struct = stt.Type.Struct(
+        types=[i64(nullable=False), boolean()],
+        nullability=stt.Type.NULLABILITY_REQUIRED,
+    )
+
+    named = named_struct(names=["index", "valid"], struct=stt.Type(struct=struct))
+    assert named
+    assert named.struct.nullability == stt.Type.NULLABILITY_REQUIRED
+    assert named.names == ["index", "valid"]
+
+
+def test_named_struct_unspecified():
+    struct = stt.Type.Struct(types=[i64(nullable=False), boolean()])
+
+    named = named_struct(names=["index", "valid"], struct=stt.Type(struct=struct))
+    assert named
+    assert named.struct.nullability == stt.Type.NULLABILITY_REQUIRED
+    assert named.names == ["index", "valid"]
+
+
+def test_named_struct_nullable():
+    struct = stt.Type.Struct(
+        types=[i64(nullable=False), boolean()],
+        nullability=stt.Type.NULLABILITY_NULLABLE,
+    )
+
+    with pytest.raises(
+        Exception, match=r"NamedStruct must not contain a nullable struct"
+    ):
+        named_struct(names=["index", "valid"], struct=stt.Type(struct=struct))