diff --git a/PocketSharp.Tests/RetrieveTests.cs b/PocketSharp.Tests/RetrieveTests.cs
index fbbb821..6858624 100644
--- a/PocketSharp.Tests/RetrieveTests.cs
+++ b/PocketSharp.Tests/RetrieveTests.cs
@@ -35,12 +35,12 @@ namespace PocketSharp.Tests
       List<PocketItem> items = await client.Retrieve(
         state: State.unread,
         tag: "pocket",
-        contentType: ContentType.article,
+        sort: Sort.title,
         since: new DateTime(2010, 12, 10),
         count: 2
       );
 
-      Assert.True(items.Count > 0);
+      Assert.InRange<int>(items.Count, 0, 2);
     }
 
 
diff --git a/PocketSharp/Models/Parameters/Parameters.cs b/PocketSharp/Models/Parameters/Parameters.cs
index 30a0e6c..b5cb013 100644
--- a/PocketSharp/Models/Parameters/Parameters.cs
+++ b/PocketSharp/Models/Parameters/Parameters.cs
@@ -35,16 +35,30 @@ namespace PocketSharp.Models
         string name = attribute.Name ?? propertyInfo.Name.ToLower();
         object value = propertyInfo.GetValue(this, null);
 
+        // invalid parameter
         if (value == null)
         {
           continue;
         }
 
+        // convert array to comma-seperated list
         if (value is IEnumerable && value.GetType().GetElementType() == typeof(string))
         {
           value = string.Join(",", ((IEnumerable)value).Cast<object>().Select(x => x.ToString()).ToArray());
         }
 
+        // convert booleans
+        if (value is bool)
+        {
+          value = System.Convert.ToBoolean(value) ? "1" : "0";
+        }
+
+        // convert DateTime to UNIX timestamp
+        if (value is DateTime)
+        {
+          value = (int)((DateTime)value - new DateTime(1970, 1, 1)).TotalSeconds;
+        }
+
         parameterDict.Add(name, value.ToString());
       }