diff --git a/SparkleShare/Mac/SparkleShare.csproj b/SparkleShare/Mac/SparkleShare.csproj
index ed607078..0b654378 100644
--- a/SparkleShare/Mac/SparkleShare.csproj
+++ b/SparkleShare/Mac/SparkleShare.csproj
@@ -52,6 +52,7 @@
     <Reference Include="MonoMac">
       <HintPath>..\..\..\monomac\src\MonoMac.dll</HintPath>
     </Reference>
+    <Reference Include="System.Web" />
   </ItemGroup>
   <ItemGroup>
     <Compile Include="AppDelegate.cs">
diff --git a/SparkleShare/SparkleInvite.cs b/SparkleShare/SparkleInvite.cs
index d3feae3d..c3a891c7 100644
--- a/SparkleShare/SparkleInvite.cs
+++ b/SparkleShare/SparkleInvite.cs
@@ -19,6 +19,7 @@ using System;
 using System.IO;
 using System.Net;
 using System.Text;
+using System.Web;
 using System.Xml;
 
 using SparkleLib;
@@ -65,7 +66,7 @@ namespace SparkleShare {
             if (string.IsNullOrEmpty (AcceptUrl))
                 return true;
 
-            string post_data   = "public_key=" + public_key;
+            string post_data   = "public_key=" + HttpUtility.UrlEncode (public_key);
             byte [] post_bytes = Encoding.UTF8.GetBytes (post_data);
 
             WebRequest request    = WebRequest.Create (AcceptUrl);
@@ -113,4 +114,4 @@ namespace SparkleShare {
             }
         }
     }
-}
+}
\ No newline at end of file