diff --git a/Recurly.Tests/BaseClientTest.cs b/Recurly.Tests/BaseClientTest.cs
index a2f0315f..6b80ff0b 100644
--- a/Recurly.Tests/BaseClientTest.cs
+++ b/Recurly.Tests/BaseClientTest.cs
@@ -78,10 +78,10 @@ public void WillAddQueryStringParameters()
         {
             var options = new RequestOptions();
             options.AddHeader("Accept-Language", "en-US");
-            var date = new DateTime(2020, 01, 01);
+            var date = DateTime.Parse("2020-01-01T08:00:00Z");
             var paramsMatcher = MockClient.QueryParameterMatcher(new Dictionary<string, object> {
                 { "param_1", "param1" },
-                { "param_2", Recurly.Utils.ISO8601(date) },
+                { "param_2", "2020-01-01T08%3A00%3A00.000Z" },
             });
 
             var client = MockClient.Build(paramsMatcher, SuccessResponse(System.Net.HttpStatusCode.OK));
diff --git a/Recurly.Tests/UtilsTest.cs b/Recurly.Tests/UtilsTest.cs
index 14ee6d6c..b71bce39 100644
--- a/Recurly.Tests/UtilsTest.cs
+++ b/Recurly.Tests/UtilsTest.cs
@@ -29,8 +29,10 @@ public void QueryString()
             d.Add("decimal", 123.456m);
             d.Add("date", new DateTime(2020, 1, 1, 0, 0, 0, DateTimeKind.Utc));
             d.Add("enum", Recurly.Tests.Constants.EnumValue.AllowedEnum);
+            d.Add("email", "testEmail@example.org");
+
             var result = Utils.QueryString(d);
-            Assert.Equal("?trueBool=true&falseBool=false&int=123&decimal=123.456&date=2020-01-01T00:00:00.000Z&enum=allowed_enum", result);
+            Assert.Equal("?trueBool=true&falseBool=false&int=123&decimal=123.456&date=2020-01-01T00%3A00%3A00.000Z&enum=allowed_enum&email=testEmail%40example.org", result);
         }
     }
 }
diff --git a/Recurly/Utils.cs b/Recurly/Utils.cs
index 3170586d..dda939f8 100644
--- a/Recurly/Utils.cs
+++ b/Recurly/Utils.cs
@@ -88,7 +88,8 @@ public static string QueryString(Dictionary<string, object> queryParams)
                     {
                         stringRepr = param.Value.ToString();
                     }
-                    qString.Add($"{param.Key}={Uri.EscapeUriString(stringRepr)}");
+
+                    qString.Add($"{param.Key}={Uri.EscapeDataString(stringRepr)}");
                 }
             }