Index: Riskeer/Common/src/Riskeer.Common.Data/AssemblyTool/AssemblyToolHelper.cs
===================================================================
diff -u -r9bb4effb0bbb67ac58342e08f78e3e8398e05bb8 -r652eb0ce8abd5c03cfa37b51b2c949c6059b3510
--- Riskeer/Common/src/Riskeer.Common.Data/AssemblyTool/AssemblyToolHelper.cs	(.../AssemblyToolHelper.cs)	(revision 9bb4effb0bbb67ac58342e08f78e3e8398e05bb8)
+++ Riskeer/Common/src/Riskeer.Common.Data/AssemblyTool/AssemblyToolHelper.cs	(.../AssemblyToolHelper.cs)	(revision 652eb0ce8abd5c03cfa37b51b2c949c6059b3510)
@@ -96,7 +96,7 @@
 
             if (!failureMechanism.InAssembly)
             {
-                return 0;
+                return double.NaN;
             }
 
             FailurePathAssemblyResult assemblyResult = failureMechanism.AssemblyResult;
Index: Riskeer/Common/test/Riskeer.Common.Data.Test/AssemblyTool/AssemblyToolHelperTest.cs
===================================================================
diff -u -rc1c8baa0d6dc754d20f83752bd08c29cdaa6fc26 -r652eb0ce8abd5c03cfa37b51b2c949c6059b3510
--- Riskeer/Common/test/Riskeer.Common.Data.Test/AssemblyTool/AssemblyToolHelperTest.cs	(.../AssemblyToolHelperTest.cs)	(revision c1c8baa0d6dc754d20f83752bd08c29cdaa6fc26)
+++ Riskeer/Common/test/Riskeer.Common.Data.Test/AssemblyTool/AssemblyToolHelperTest.cs	(.../AssemblyToolHelperTest.cs)	(revision 652eb0ce8abd5c03cfa37b51b2c949c6059b3510)
@@ -129,7 +129,7 @@
         }
 
         [Test]
-        public void AssembleFailureMechanism_WithFailurePathInAssemblyFalse_ReturnsZero()
+        public void AssembleFailureMechanism_WithFailurePathInAssemblyFalse_ReturnsNaN()
         {
             // Setup
             var random = new Random(21);
@@ -145,7 +145,7 @@
                 failurePath, sr => null, random.NextDouble());
 
             // Assert
-            Assert.AreEqual(0, assemblyResult);
+            Assert.IsNaN(assemblyResult);
             mocks.VerifyAll();
         }