diff --git a/OSCADSharp/OSCADSharp.UnitTests/OSCADSharp.UnitTests.csproj b/OSCADSharp/OSCADSharp.UnitTests/OSCADSharp.UnitTests.csproj
index bbd7d8c..566ba5d 100644
--- a/OSCADSharp/OSCADSharp.UnitTests/OSCADSharp.UnitTests.csproj
+++ b/OSCADSharp/OSCADSharp.UnitTests/OSCADSharp.UnitTests.csproj
@@ -56,6 +56,7 @@
     <Compile Include="OSCADObjectTests.cs" />
     <Compile Include="SphereTests.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
+    <Compile Include="UnionTests.cs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\OSCADSharp\OSCADSharp.csproj">
diff --git a/OSCADSharp/OSCADSharp.UnitTests/UnionTests.cs b/OSCADSharp/OSCADSharp.UnitTests/UnionTests.cs
new file mode 100644
index 0000000..487d0c7
--- /dev/null
+++ b/OSCADSharp/OSCADSharp.UnitTests/UnionTests.cs
@@ -0,0 +1,52 @@
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using OSCADSharp.Solids;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace OSCADSharp.UnitTests
+{
+    [TestClass]
+    public class UnionTests
+    {
+        [TestMethod]
+        public void Union_AffectedObjectsAreChildren()
+        {
+            var union = new Cube().Union(new Cylinder());
+            var children = union.Children();
+
+            Assert.IsTrue(children.ElementAt(0).GetType() == typeof(Cube));
+            Assert.IsTrue(children.ElementAt(1).GetType() == typeof(Cylinder));
+        }
+
+        [TestMethod]
+        public void Union_AffectedObjectsAreInOutputScript()
+        {
+            var union = new Cube().Union(new Cylinder());
+            string script = union.ToString();
+
+            Assert.IsTrue(script.Contains("cube("));
+            Assert.IsTrue(script.Contains("cylinder("));
+        }
+
+        [TestMethod]
+        public void Union_FirstStatementInOutputScriptIsUnionMethodCall()
+        {
+            var union = new Cube().Union(new Cylinder());
+            string script = union.ToString();
+
+            Assert.IsTrue(script.StartsWith("union()"));
+        }
+
+        [TestMethod]
+        public void Union_FirstElementAppearsFirstInOutputScript()
+        {
+            var union = new Cube().Union(new Cylinder());
+            string script = union.ToString();
+
+            Assert.IsTrue(script.IndexOf("cube(") < script.IndexOf("cylinder("));
+        }
+    }
+}
diff --git a/OSCADSharp/OSCADSharp/OSCADObject.cs b/OSCADSharp/OSCADSharp/OSCADObject.cs
index f7ddbaa..fa32235 100644
--- a/OSCADSharp/OSCADSharp/OSCADObject.cs
+++ b/OSCADSharp/OSCADSharp/OSCADObject.cs
@@ -233,7 +233,9 @@ namespace OSCADSharp
         /// <returns></returns>
         public IEnumerable<OSCADObject> Children()
         {
-            Stack<OSCADObject> toTraverse = new Stack<OSCADObject>(this.children);
+            // Initial children are reversed here because for objects with multiple children (such as boolean operations)
+            // the natural collection order would yield opposite the expected order in a stack (first child would be the last popped)
+            Stack<OSCADObject> toTraverse = new Stack<OSCADObject>(this.children.Reverse<OSCADObject>());
             List<OSCADObject> allChildren = new List<OSCADObject>();
             OSCADObject child = null;