diff --git a/Common/src/main/java/at/petrak/hexcasting/api/item/IotaHolderItem.java b/Common/src/main/java/at/petrak/hexcasting/api/item/IotaHolderItem.java
index 62f2aade..11e9bf70 100644
--- a/Common/src/main/java/at/petrak/hexcasting/api/item/IotaHolderItem.java
+++ b/Common/src/main/java/at/petrak/hexcasting/api/item/IotaHolderItem.java
@@ -86,12 +86,18 @@ public interface IotaHolderItem {
         return HexIotaTypes.getColor(tag);
     }
 
+    /**
+     * Write {@code null} to indicate erasing
+     */
     boolean canWrite(ItemStack stack, @Nullable Iota iota);
 
+    /**
+     * Write {@code null} to indicate erasing
+     */
     void writeDatum(ItemStack stack, @Nullable Iota iota);
 
     static void appendHoverText(IotaHolderItem self, ItemStack stack, List<Component> components,
-        TooltipFlag flag) {
+                                TooltipFlag flag) {
         var datumTag = self.readIotaTag(stack);
         if (datumTag != null) {
             var cmp = HexIotaTypes.getDisplay(datumTag);
diff --git a/Common/src/main/java/at/petrak/hexcasting/common/items/ItemSlate.java b/Common/src/main/java/at/petrak/hexcasting/common/items/ItemSlate.java
index c6faf57b..8d97a5da 100644
--- a/Common/src/main/java/at/petrak/hexcasting/common/items/ItemSlate.java
+++ b/Common/src/main/java/at/petrak/hexcasting/common/items/ItemSlate.java
@@ -86,7 +86,10 @@ public class ItemSlate extends BlockItem implements IotaHolderItem {
 
     @Override
     public boolean canWrite(ItemStack stack, Iota datum) {
-        return datum instanceof PatternIota && !NBTHelper.hasCompound(stack, BlockEntitySlate.TAG_PATTERN);
+        var isWritten = NBTHelper.hasCompound(stack, "BlockEntityTag")
+            && stack.getTag().getCompound("BlockEntityTag").contains(BlockEntitySlate.TAG_PATTERN);
+        return (datum instanceof PatternIota && !isWritten)
+            || (datum == null && isWritten);
     }
 
     @Override