diff --git a/MCGalaxy/Commands/building/CmdReplaceBrush.cs b/MCGalaxy/Commands/building/CmdReplaceBrush.cs
index ad4173212..5a1dca3af 100644
--- a/MCGalaxy/Commands/building/CmdReplaceBrush.cs
+++ b/MCGalaxy/Commands/building/CmdReplaceBrush.cs
@@ -30,40 +30,58 @@ namespace MCGalaxy.Commands.Building {
         public override void Use(Player p, string message) {
             if (message == "") { Help(p); return; }
             if (Player.IsSuper(p)) { MessageInGameOnly(p); return; }
+            
             string replaceCmd = ReplaceNot ? "replacenot" : "replace";
             if (!p.group.CanExecute(replaceCmd) || !p.group.CanExecute("brush")) {
                 Player.Message(p, "You cannot use /brush and/or /" + replaceCmd + 
                                    ", so therefore cannot use this command."); return;
             }
             
+            message = message.ToLower();
+            string[] parts = message.SplitSpaces(3);
+            if (!ValidateArgs(p, parts)) return;
+ 
             Player.Message(p, "Place two blocks to determine the edges.");
-            p.MakeSelection(2, message.ToLower(), DoReplace);
+            p.MakeSelection(2, message, DoReplace);
         }
         
-        bool DoReplace(Player p, Vec3S32[] marks, object state, byte type, byte extType) {
-            string[] parts = ((string)state).SplitSpaces(3);
-            if (parts.Length < 2) { Help(p); return false; }
+        bool ValidateArgs(Player p, string[] args) {
+            if (args.Length < 2) { Help(p); return false; }
             
             byte extBlock = 0;
-            int block = DrawCmd.GetBlockIfAllowed(p, parts[0], out extBlock);
+            int block = DrawCmd.GetBlockIfAllowed(p, args[0], out extBlock);
             if (block == -1) return false;
             
-            BrushFactory factory = BrushFactory.Find(parts[1]);
+            BrushFactory factory = BrushFactory.Find(args[1]);
             if (factory == null) {
-                Player.Message(p, "No brush found with name \"{0}\".", parts[1]);
+                Player.Message(p, "No brush found with name \"{0}\".", args[1]);
                 Player.Message(p, "Available brushes: " + BrushFactory.Available);
                 return false;
             }
-
-            string brushMessage = parts.Length > 2 ? parts[2].ToLower() : "";
-            BrushArgs args = new BrushArgs(p, brushMessage, type, extType);
-            Brush brush = factory.Construct(args);
+            
+            string brushMessage = args.Length > 2 ? args[2] : "";
+            byte held, extHeld;
+            held = p.GetActualHeldBlock(out extHeld);
+            BrushArgs bArgs = new BrushArgs(p, brushMessage, held, extHeld);
+            return factory.Validate(bArgs);
+        }
+        
+        bool DoReplace(Player p, Vec3S32[] marks, object state, byte type, byte extType) {
+            string[] args = ((string)state).SplitSpaces(3);
+            byte extBlock = 0;
+            int block = DrawCmd.GetBlockIfAllowed(p, args[0], out extBlock);
+            if (block == -1) return false;
+            
+            BrushFactory factory = BrushFactory.Find(args[1]);
+            string brushMessage = args.Length > 2 ? args[2] : "";
+            BrushArgs bArgs = new BrushArgs(p, brushMessage, type, extType);
+            Brush brush = factory.Construct(bArgs);
             if (brush == null) return false;
             
-            DrawOp drawOp = null;
-            if (ReplaceNot) drawOp = new ReplaceNotDrawOp((byte)block, extBlock);
-            else drawOp = new ReplaceDrawOp((byte)block, extBlock);
-            return DrawOp.DoDrawOp(drawOp, brush, p, marks);
+            DrawOp op = null;
+            if (ReplaceNot) op = new ReplaceNotDrawOp((byte)block, extBlock);
+            else op = new ReplaceDrawOp((byte)block, extBlock);
+            return DrawOp.DoDrawOp(op, brush, p, marks);
         }
         
         protected virtual bool ReplaceNot { get { return false; } }
diff --git a/MCGalaxy/Commands/building/ReplaceCmd.cs b/MCGalaxy/Commands/building/ReplaceCmd.cs
index e7f4cf605..cd0678af4 100644
--- a/MCGalaxy/Commands/building/ReplaceCmd.cs
+++ b/MCGalaxy/Commands/building/ReplaceCmd.cs
@@ -29,6 +29,14 @@ namespace MCGalaxy.Commands.Building {
         protected virtual bool ReplaceNot { get { return false; } }
         
         public override void Use(Player p, string message) {
+            string brushMsg = message.ToLower();
+            byte block, extBlock;
+            block = p.GetActualHeldBlock(out extBlock);
+            
+            BrushArgs args = new BrushArgs(p, brushMsg, block, extBlock);
+            string name = ReplaceNot ? "replacenot" : "replace";
+            if (!BrushFactory.Find(name).Validate(args)) return;
+            
             Player.Message(p, "Place two blocks to determine the edges.");
             p.MakeSelection(2, message.ToLower(), DoReplace);
         }