diff --git a/src/Discord.Net.Commands/Extensions/MessageExtensions.cs b/src/Discord.Net.Commands/Extensions/MessageExtensions.cs
index c4e4a2c07..f880e1d98 100644
--- a/src/Discord.Net.Commands/Extensions/MessageExtensions.cs
+++ b/src/Discord.Net.Commands/Extensions/MessageExtensions.cs
@@ -60,10 +60,5 @@ namespace Discord.Commands
             }
             return false;
         }
-        /// <summary>
-        ///     Gets wheter the message's attachments are spoilers or not.
-        /// </summary>
-        public static bool IsSpoiler(this IAttachment attachment)
-            => attachment.Filename.StartsWith("SPOILER_");
     }
 }
diff --git a/src/Discord.Net.Core/Entities/Messages/IAttachment.cs b/src/Discord.Net.Core/Entities/Messages/IAttachment.cs
index 655777998..938ad4495 100644
--- a/src/Discord.Net.Core/Entities/Messages/IAttachment.cs
+++ b/src/Discord.Net.Core/Entities/Messages/IAttachment.cs
@@ -5,6 +5,11 @@ namespace Discord
     /// </summary>
     public interface IAttachment
     {
+        /// <summary>
+        ///     The prefix applied to files to indicate that it is a spoiler.
+        /// </summary>
+        public const string SpoilerPrefix = "SPOILER_";
+
         /// <summary>
         ///     Gets the ID of this attachment.
         /// </summary>
diff --git a/src/Discord.Net.Core/Extensions/AttachmentExtensions.cs b/src/Discord.Net.Core/Extensions/AttachmentExtensions.cs
new file mode 100644
index 000000000..8a9e18dbf
--- /dev/null
+++ b/src/Discord.Net.Core/Extensions/AttachmentExtensions.cs
@@ -0,0 +1,11 @@
+namespace Discord
+{
+    public static class AttachmentExtensions
+    {
+        /// <summary>
+        ///     Gets wheter the message's attachments are spoilers or not.
+        /// </summary>
+        public static bool IsSpoiler(this IAttachment attachment)
+            => attachment.Filename.StartsWith(IAttachment.SpoilerPrefix);
+    }
+}
diff --git a/src/Discord.Net.Rest/API/Rest/UploadFileParams.cs b/src/Discord.Net.Rest/API/Rest/UploadFileParams.cs
index 93d9247e9..28772356d 100644
--- a/src/Discord.Net.Rest/API/Rest/UploadFileParams.cs
+++ b/src/Discord.Net.Rest/API/Rest/UploadFileParams.cs
@@ -30,8 +30,8 @@ namespace Discord.API.Rest
         {
             var d = new Dictionary<string, object>();
             var filename = Filename.GetValueOrDefault("unknown.dat");
-            if (IsSpoiler && !filename.StartsWith("SPOILER_"))
-                filename = filename.Insert(0, "SPOILER_");
+            if (IsSpoiler && !filename.StartsWith(IAttachment.SpoilerPrefix))
+                filename = filename.Insert(0, IAttachment.SpoilerPrefix);
             d["file"] = new MultipartFile(File, filename);
 
             var payload = new Dictionary<string, object>();