diff --git a/Data_Eval/Data_Eval/Data_Eval.csproj b/Data_Eval/Data_Eval/Data_Eval.csproj
index 20081b1..15d7997 100644
--- a/Data_Eval/Data_Eval/Data_Eval.csproj
+++ b/Data_Eval/Data_Eval/Data_Eval.csproj
@@ -7,7 +7,7 @@
     <SignAssembly>true</SignAssembly>
     <DelaySign>false</DelaySign>
     <AssemblyOriginatorKeyFile>Data_Eval.snk</AssemblyOriginatorKeyFile>
-    <Version>2.4.3</Version>
+    <Version>2.4.4</Version>
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|AnyCPU'">
diff --git a/Data_Eval/Data_Eval/Data_Eval.nuspec b/Data_Eval/Data_Eval/Data_Eval.nuspec
index acfdefc..319a1b2 100644
--- a/Data_Eval/Data_Eval/Data_Eval.nuspec
+++ b/Data_Eval/Data_Eval/Data_Eval.nuspec
@@ -2,7 +2,7 @@
 <package>
 	<metadata>
 		<id>Data.Eval</id>
-		<version>2.4.3</version>
+		<version>2.4.4</version>
 		<title>Data.Eval</title>
 		<authors>Bruce Dunwiddie</authors>
 		<owners>shriop</owners>
diff --git a/Data_Eval/Data_Eval/Evaluator.cs b/Data_Eval/Data_Eval/Evaluator.cs
index 4dab68b..6572c1c 100644
--- a/Data_Eval/Data_Eval/Evaluator.cs
+++ b/Data_Eval/Data_Eval/Evaluator.cs
@@ -321,6 +321,13 @@ private void InitExec(string caller)
 			{
 				references.Add(caller);
 
+				// add references to containing assemblies for all used variable types
+				variables
+					.Select(v => v.Value.Type.Assembly.Location)
+					.Distinct()
+					.ToList()
+					.ForEach(a => references.Add(a));
+
 				execution = new Execution();
 
 				Compiler compiler = new Compiler();
diff --git a/Data_Eval/Tests/EvaluatorTests.cs b/Data_Eval/Tests/EvaluatorTests.cs
index 4492026..ee7ae22 100644
--- a/Data_Eval/Tests/EvaluatorTests.cs
+++ b/Data_Eval/Tests/EvaluatorTests.cs
@@ -181,5 +181,19 @@ public void Evaluator_DynamicVariable()
 
 			Assert.AreEqual("something", evaluator.Eval<string>());
 		}
+
+		[Test]
+		public void Evaluator_NullVariableComparison()
+		{
+			var evaluator = new Evaluator(
+				"return test == null");
+
+			evaluator.SetVariable(
+				"test",
+				null,
+				typeof(string));
+
+			Assert.IsTrue(evaluator.Eval<bool>());
+		}
 	}
 }