diff --git a/src/main/java/com/sk89q/worldedit/WorldEdit.java b/src/main/java/com/sk89q/worldedit/WorldEdit.java
index 617618100..6338fa6d9 100644
--- a/src/main/java/com/sk89q/worldedit/WorldEdit.java
+++ b/src/main/java/com/sk89q/worldedit/WorldEdit.java
@@ -570,7 +570,7 @@ public BaseBlock getBlock(LocalPlayer player, String arg,
                                 else skullType = 3;
                             }
                             if (skullType == 3) {
-                                return new SkullBlock(data, rot, type);
+                                return new SkullBlock(data, rot, type.replace(" ", "_")); // valid MC usernames
                             } else {
                                 return new SkullBlock(data, skullType, rot);
                             }