diff --git a/SparkleShare/SparkleAvatars.cs b/SparkleShare/SparkleAvatars.cs
index b4ff65b5..b735bc51 100644
--- a/SparkleShare/SparkleAvatars.cs
+++ b/SparkleShare/SparkleAvatars.cs
@@ -34,7 +34,10 @@ namespace SparkleShare
 
         public static string GetAvatar (string email, int size, string target_path)
         {
+            #if __MonoCS__
             ServicePointManager.ServerCertificateValidationCallback = GetAvatarValidationCallBack;
+            #endif
+
             email = email.ToLower ();
             
             if (skipped_avatars.Contains (email))
diff --git a/SparkleShare/SparkleInvite.cs b/SparkleShare/SparkleInvite.cs
index e4bbcafa..7ce67eb9 100644
--- a/SparkleShare/SparkleInvite.cs
+++ b/SparkleShare/SparkleInvite.cs
@@ -60,7 +60,11 @@ namespace SparkleShare {
 
         public bool Accept (string public_key)
         {
-            ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };
+            #if __MonoCS__
+            ServicePointManager.ServerCertificateValidationCallback = delegate {
+                return true;
+            };
+            #endif
 
             if (string.IsNullOrEmpty (AcceptUrl))
                 return true;