diff --git a/app/styles/play/level/tome/spell.sass b/app/styles/play/level/tome/spell.sass
index b7d2b3169..964288585 100644
--- a/app/styles/play/level/tome/spell.sass
+++ b/app/styles/play/level/tome/spell.sass
@@ -107,6 +107,9 @@
     .executed
       background-color: rgba(110, 110, 110, 0.12)
 
+    .locked-code
+      border: 1px dashed rgba(53, 45, 34, 0.5)
+
     +keyframes(pulseRedBackground)
       from
         background-color: rgba(255, 45, 27, 0.4)
diff --git a/app/views/play/level/tome/SpellView.coffee b/app/views/play/level/tome/SpellView.coffee
index fa5610bda..06d948f6d 100644
--- a/app/views/play/level/tome/SpellView.coffee
+++ b/app/views/play/level/tome/SpellView.coffee
@@ -293,10 +293,16 @@ module.exports = class SpellView extends CocoView
         wrapper => orig.apply obj, args
       obj[method]
 
+    if @lockedCodeMarkerID?
+      @aceSession.removeMarker @lockedCodeMarkerID
+      @lockedCodeMarkerID = null
+
     @readOnlyRanges = []
     lines = @aceDoc.getAllLines()
     lastRow = row for line, row in lines when not /^\s*$/.test(line)
-    @readOnlyRanges.push new Range 0, 0, lastRow, lines[lastRow].length - 1 if lastRow?
+    if lastRow?
+      @readOnlyRanges.push new Range 0, 0, lastRow, lines[lastRow].length - 1
+      @lockedCodeMarkerID = @aceSession.addMarker @readOnlyRanges[0], 'locked-code', 'fullLine'
 
     # Override write operations that intersect with default code
     interceptCommand @ace, 'onPaste', preventReadonly