diff --git a/Queste.Test/ErrorTests.cs b/Queste.Test/ErrorTests.cs
index d364adf..2a1652c 100644
--- a/Queste.Test/ErrorTests.cs
+++ b/Queste.Test/ErrorTests.cs
@@ -17,9 +17,9 @@ public class ErrorTests
     [InlineData("      \n")]
     [InlineData("      \r\n")]
     [InlineData(null)]
-    public void ExpressionShouldReturnNull1(string queryString)
+    public void ExpressionShouldNotReturnNull1(string queryString)
     {
-      ExpressionBuilder.BuildExpression<KeyValuePair<string, DateTime>>(queryString).Should().BeNull();
+      ExpressionBuilder.BuildExpression<KeyValuePair<string, DateTime>>(queryString).Should().NotBeNull();
     }
 
     [Theory]
@@ -32,9 +32,9 @@ public void ExpressionShouldReturnNull1(string queryString)
     [InlineData("      \n")]
     [InlineData("      \r\n")]
     [InlineData(null)]
-    public void FunctionShouldReturnNull1(string queryString)
+    public void FunctionShouldNotReturnNull1(string queryString)
     {
-      ExpressionBuilder.BuildFunction<KeyValuePair<string, DateTime>>(queryString).Should().BeNull();
+      ExpressionBuilder.BuildFunction<KeyValuePair<string, DateTime>>(queryString).Should().NotBeNull();
     }
 
     [Theory]
diff --git a/Queste/ExpressionBuilder.cs b/Queste/ExpressionBuilder.cs
index 8724af2..1f56660 100644
--- a/Queste/ExpressionBuilder.cs
+++ b/Queste/ExpressionBuilder.cs
@@ -23,7 +23,7 @@ public static class ExpressionBuilder
     {
       if (string.IsNullOrWhiteSpace(queryString))
       {
-        return null;
+        return p => false;
       }
 
       queryString = queryString.Replace("%3d", "=");
diff --git a/Queste/Properties/AssemblyInfo.cs b/Queste/Properties/AssemblyInfo.cs
index 94b19ee..4ed16ec 100644
--- a/Queste/Properties/AssemblyInfo.cs
+++ b/Queste/Properties/AssemblyInfo.cs
@@ -31,5 +31,5 @@
 // You can specify all the values or you can default the Build and Revision Numbers 
 // by using the '*' as shown below:
 // [assembly: AssemblyVersion("1.0.*")]
-[assembly: AssemblyVersion("1.8.0.0")]
-[assembly: AssemblyFileVersion("1.8.0.0")]
+[assembly: AssemblyVersion("1.9.0.0")]
+[assembly: AssemblyFileVersion("1.9.0.0")]