diff --git a/src/Target/Php/Transpiler/TypeReference/TypeReferenceTranspiler.php b/src/Target/Php/Transpiler/TypeReference/TypeReferenceTranspiler.php
index af5a7326..1a3df137 100644
--- a/src/Target/Php/Transpiler/TypeReference/TypeReferenceTranspiler.php
+++ b/src/Target/Php/Transpiler/TypeReference/TypeReferenceTranspiler.php
@@ -27,10 +27,13 @@
 use PackageFactory\ComponentEngine\TypeSystem\Type\BooleanType\BooleanType;
 use PackageFactory\ComponentEngine\TypeSystem\Type\ComponentType\ComponentType;
 use PackageFactory\ComponentEngine\TypeSystem\Type\EnumType\EnumType;
+use PackageFactory\ComponentEngine\TypeSystem\Type\NullType\NullType;
 use PackageFactory\ComponentEngine\TypeSystem\Type\NumberType\NumberType;
 use PackageFactory\ComponentEngine\TypeSystem\Type\SlotType\SlotType;
 use PackageFactory\ComponentEngine\TypeSystem\Type\StringType\StringType;
 use PackageFactory\ComponentEngine\TypeSystem\Type\StructType\StructType;
+use PackageFactory\ComponentEngine\TypeSystem\Type\UnionType\UnionType;
+use PackageFactory\ComponentEngine\TypeSystem\TypeInterface;
 
 final class TypeReferenceTranspiler
 {
@@ -43,7 +46,34 @@ public function __construct(
     public function transpile(TypeReferenceNode $typeReferenceNode): string
     {
         $type = $this->scope->resolveTypeReference($typeReferenceNode);
-        $phpTypeReference = match ($type::class) {
+
+        return match ($type::class) {
+            UnionType::class => $this->transpileUnionType($type, $typeReferenceNode),
+            default => $this->transpileNonUnionType($type, $typeReferenceNode)
+        };
+    }
+    
+    private function transpileUnionType(UnionType $unionType, TypeReferenceNode $typeReferenceNode): string
+    {
+        if (count($unionType->members) === 2) {
+            $otherTypeIfTypeIsNullable = match (true) {
+                $unionType->members[0]->is(NullType::get()) => $unionType->members[1],
+                $unionType->members[1]->is(NullType::get()) => $unionType->members[0],
+                default => null
+            };
+
+            if ($otherTypeIfTypeIsNullable) {
+                return $this->transpileNullableType($otherTypeIfTypeIsNullable, $typeReferenceNode);
+            }
+        }
+
+        throw new \Exception('@TODO Transpilation of complex union types is not implemented');
+        
+    }
+    
+    private function transpileNonUnionType(TypeInterface $type, TypeReferenceNode $typeReferenceNode): string
+    {
+        return match ($type::class) {
             NumberType::class => 'int|float',
             StringType::class => 'string',
             BooleanType::class => 'bool',
@@ -51,14 +81,16 @@ public function transpile(TypeReferenceNode $typeReferenceNode): string
             ComponentType::class => $this->strategy->getPhpTypeReferenceForComponentType($type, $typeReferenceNode),
             EnumType::class => $this->strategy->getPhpTypeReferenceForEnumType($type, $typeReferenceNode),
             StructType::class => $this->strategy->getPhpTypeReferenceForStructType($type, $typeReferenceNode),
+            UnionType::class => throw new \Exception("There is no such thing as nested unions, think again."),
             default => $this->strategy->getPhpTypeReferenceForCustomType($type, $typeReferenceNode)
         };
+    }
 
-        return $typeReferenceNode->isOptional
-            ? match ($phpTypeReference) {
-                'int|float' => 'null|int|float',
-                default => '?' . $phpTypeReference
-            }
-            : $phpTypeReference;
+    private function transpileNullableType(TypeInterface $type, TypeReferenceNode $typeReferenceNode): string
+    {
+        if ($type->is(NumberType::get())) {
+            return 'null|int|float';
+        }
+        return '?' . $this->transpileNonUnionType($type, $typeReferenceNode);
     }
 }
diff --git a/src/TypeSystem/Scope/GlobalScope/GlobalScope.php b/src/TypeSystem/Scope/GlobalScope/GlobalScope.php
index a6ab1b87..ada0f5cb 100644
--- a/src/TypeSystem/Scope/GlobalScope/GlobalScope.php
+++ b/src/TypeSystem/Scope/GlobalScope/GlobalScope.php
@@ -22,13 +22,14 @@
 
 namespace PackageFactory\ComponentEngine\TypeSystem\Scope\GlobalScope;
 
-use PackageFactory\ComponentEngine\Parser\Ast\ComponentDeclarationNode;
 use PackageFactory\ComponentEngine\Parser\Ast\TypeReferenceNode;
 use PackageFactory\ComponentEngine\TypeSystem\ScopeInterface;
 use PackageFactory\ComponentEngine\TypeSystem\Type\BooleanType\BooleanType;
+use PackageFactory\ComponentEngine\TypeSystem\Type\NullType\NullType;
 use PackageFactory\ComponentEngine\TypeSystem\Type\NumberType\NumberType;
 use PackageFactory\ComponentEngine\TypeSystem\Type\SlotType\SlotType;
 use PackageFactory\ComponentEngine\TypeSystem\Type\StringType\StringType;
+use PackageFactory\ComponentEngine\TypeSystem\Type\UnionType\UnionType;
 use PackageFactory\ComponentEngine\TypeSystem\TypeInterface;
 
 final class GlobalScope implements ScopeInterface
@@ -51,12 +52,16 @@ public function lookupTypeFor(string $name): ?TypeInterface
 
     public function resolveTypeReference(TypeReferenceNode $typeReferenceNode): TypeInterface
     {
-        return match ($typeReferenceNode->name) {
+        $type = match ($typeReferenceNode->name) {
             'string' => StringType::get(),
             'number' => NumberType::get(),
             'boolean' => BooleanType::get(),
             'slot' => SlotType::get(),
             default => throw new \Exception('@TODO: Unknown Type ' . $typeReferenceNode->name)
         };
+        if ($typeReferenceNode->isOptional) {
+            $type = UnionType::of($type, NullType::get());
+        }
+        return $type;
     }
 }
diff --git a/src/TypeSystem/Scope/ModuleScope/ModuleScope.php b/src/TypeSystem/Scope/ModuleScope/ModuleScope.php
index 034da99e..80748ea2 100644
--- a/src/TypeSystem/Scope/ModuleScope/ModuleScope.php
+++ b/src/TypeSystem/Scope/ModuleScope/ModuleScope.php
@@ -26,6 +26,8 @@
 use PackageFactory\ComponentEngine\Parser\Ast\ModuleNode;
 use PackageFactory\ComponentEngine\Parser\Ast\TypeReferenceNode;
 use PackageFactory\ComponentEngine\TypeSystem\ScopeInterface;
+use PackageFactory\ComponentEngine\TypeSystem\Type\NullType\NullType;
+use PackageFactory\ComponentEngine\TypeSystem\Type\UnionType\UnionType;
 use PackageFactory\ComponentEngine\TypeSystem\TypeInterface;
 
 final class ModuleScope implements ScopeInterface
@@ -45,7 +47,11 @@ public function lookupTypeFor(string $name): ?TypeInterface
     public function resolveTypeReference(TypeReferenceNode $typeReferenceNode): TypeInterface
     {
         if ($importNode = $this->moduleNode->imports->get($typeReferenceNode->name)) {
-            return $this->loader->resolveTypeOfImport($importNode);
+            $type = $this->loader->resolveTypeOfImport($importNode);
+            if ($typeReferenceNode->isOptional) {
+                $type = UnionType::of($type, NullType::get());
+            }
+            return $type;
         }
 
         if ($this->parentScope) {
diff --git a/src/TypeSystem/Type/UnionType/UnionType.php b/src/TypeSystem/Type/UnionType/UnionType.php
index 64e1f0cb..fe6b1c7f 100644
--- a/src/TypeSystem/Type/UnionType/UnionType.php
+++ b/src/TypeSystem/Type/UnionType/UnionType.php
@@ -29,7 +29,7 @@ final class UnionType implements TypeInterface
     /**
      * @var TypeInterface[]
      */
-    private array $members;
+    public array $members;
 
     private function __construct(TypeInterface ...$members)
     {
diff --git a/test/Unit/TypeSystem/Scope/Fixtures/DummyScope.php b/test/Unit/TypeSystem/Scope/Fixtures/DummyScope.php
index 954a1f3c..cb3440b9 100644
--- a/test/Unit/TypeSystem/Scope/Fixtures/DummyScope.php
+++ b/test/Unit/TypeSystem/Scope/Fixtures/DummyScope.php
@@ -24,6 +24,8 @@
 
 use PackageFactory\ComponentEngine\Parser\Ast\TypeReferenceNode;
 use PackageFactory\ComponentEngine\TypeSystem\ScopeInterface;
+use PackageFactory\ComponentEngine\TypeSystem\Type\NullType\NullType;
+use PackageFactory\ComponentEngine\TypeSystem\Type\UnionType\UnionType;
 use PackageFactory\ComponentEngine\TypeSystem\TypeInterface;
 
 final class DummyScope implements ScopeInterface
@@ -46,6 +48,9 @@ public function lookupTypeFor(string $name): ?TypeInterface
     public function resolveTypeReference(TypeReferenceNode $typeReferenceNode): TypeInterface
     {
         if ($type = $this->typeNameToTypeMap[$typeReferenceNode->name] ?? null) {
+            if ($typeReferenceNode->isOptional) {
+                $type = UnionType::of($type, NullType::get());
+            }
             return $type;
         }