diff --git a/src/TypeDef.php b/src/TypeDef.php
index c3da488..9fa1c99 100644
--- a/src/TypeDef.php
+++ b/src/TypeDef.php
@@ -21,7 +21,7 @@ class TypeDef
      *
      * @var array<array<string>>
      */
-    private array $type = [[]];
+    protected array $type = [[]];
 
     public readonly bool $allowsNull;
 
@@ -71,6 +71,16 @@ public function getSimpleType(): ?string
         return $this->isSimple() ? $this->type[0][0] : null;
     }
 
+    /**
+     * Returns a list of the unioned types, or null if it's not a union type.
+     *
+     * @return string[]|null
+     */
+    public function getUnionTypes(): ?array
+    {
+        return $this->complexity === TypeComplexity::Union ? array_column($this->type, 0) : null;
+    }
+
     /**
      * Determines if this type definition will accept a value of the specified type.
      *
diff --git a/tests/TypeDefTest.php b/tests/TypeDefTest.php
index d2d5405..8347168 100644
--- a/tests/TypeDefTest.php
+++ b/tests/TypeDefTest.php
@@ -151,6 +151,7 @@ public static function typeDefProvider(): iterable
                 static::assertFalse($typeDef->allowsNull);
                 static::assertFalse($typeDef->isSimple());
                 static::assertEquals(TypeComplexity::Union, $typeDef->complexity);
+                static::assertEquals(['string', 'int'], $typeDef->getUnionTypes());
                 static::assertTrue($typeDef->accepts('int'));
                 static::assertTrue($typeDef->accepts('string'));
                 static::assertFalse($typeDef->accepts(SomeClass::class));
@@ -163,6 +164,7 @@ public static function typeDefProvider(): iterable
                 static::assertFalse($typeDef->allowsNull);
                 static::assertFalse($typeDef->isSimple());
                 static::assertEquals(TypeComplexity::Union, $typeDef->complexity);
+                static::assertEquals([SomeClass::class, 'string'], $typeDef->getUnionTypes());
                 static::assertTrue($typeDef->accepts(SomeClass::class));
                 static::assertTrue($typeDef->accepts('string'));
                 static::assertFalse($typeDef->accepts(OtherClass::class));