diff --git a/HISTORY.md b/HISTORY.md
index f575970c..69dee39a 100755
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -1,6 +1,8 @@
 # Snap! (BYOB) History
 
 ## in development:
+* **New Features:**
+    * you can now also "peel off" custom block instances from their prototype templates in the block editor
 * **Notable Changes:**
     * speed-up  talk bubble positioning by 5x
 * **Notable Fixes:**
@@ -9,7 +11,8 @@
 
 ### 2021-04-17
 * objects: fixed an occasional rendering glitch when changing the display style of a variable watcher
-* objects: tweaked CellMorph shadow rendering 
+* objects: tweaked CellMorph shadow rendering
+* byob: enable "peeling off" custom block instances from their prototype templates
 
 ### 2021-04-17
 * new dev version
diff --git a/snap.html b/snap.html
index 8f7157c2..d1998ca9 100755
--- a/snap.html
+++ b/snap.html
@@ -14,7 +14,7 @@
         <script src="src/gui.js?version=2021-04-17"></script>
         <script src="src/paint.js?version=2020-05-17"></script>
         <script src="src/lists.js?version=2021-03-15"></script>
-        <script src="src/byob.js?version=2021-03-05"></script>
+        <script src="src/byob.js?version=2021-04-20"></script>
         <script src="src/tables.js?version=2021-03-05"></script>
         <script src="src/sketch.js?version=2020-07-13"></script>
         <script src="src/video.js?version=2019-06-27"></script>
diff --git a/src/byob.js b/src/byob.js
index 9dc8d4de..f9cffb7c 100644
--- a/src/byob.js
+++ b/src/byob.js
@@ -106,7 +106,7 @@ WatcherMorph, XML_Serializer, SnapTranslator*/
 
 // Global stuff ////////////////////////////////////////////////////////
 
-modules.byob = '2021-March-05';
+modules.byob = '2021-April-20';
 
 // Declarations
 
@@ -645,6 +645,9 @@ CustomCommandBlockMorph.prototype.init = function (definition, isProto) {
     this.isGlobal = definition ? definition.isGlobal : false;
     this.isPrototype = isProto || false; // optional
     CustomCommandBlockMorph.uber.init.call(this);
+    if (isProto) {
+        this.isTemplate = true;
+    }
     this.category = definition.category;
     this.selector = 'evaluateCustomBlock';
     this.variables = null;
@@ -655,6 +658,17 @@ CustomCommandBlockMorph.prototype.init = function (definition, isProto) {
     }
 };
 
+CustomCommandBlockMorph.prototype.reactToTemplateCopy = function () {
+    var def;
+    if (this.isPrototype) {
+        def = this.definition;
+        this.isPrototype = false;
+        this.refresh();
+        this.refreshDefaults(def);
+    }
+    CustomCommandBlockMorph.uber.reactToTemplateCopy.call(this);
+};
+
 CustomCommandBlockMorph.prototype.initializeVariables = function (oldVars) {
     this.variables = new VariableFrame();
     if (!this.isGlobal) {
@@ -1413,6 +1427,9 @@ CustomReporterBlockMorph.prototype.init = function (
     this.isGlobal = definition ? definition.isGlobal : false;
     this.isPrototype = isProto || false; // optional
     CustomReporterBlockMorph.uber.init.call(this, isPredicate, true); // sil.
+    if (isProto) {
+        this.isTemplate = true;
+    }
     this.category = definition.category;
     this.storedTranslations = null; // transient - only for "wishes"
     this.variables = new VariableFrame();
@@ -1426,6 +1443,9 @@ CustomReporterBlockMorph.prototype.init = function (
 CustomReporterBlockMorph.prototype.initializeVariables =
     CustomCommandBlockMorph.prototype.initializeVariables;
 
+CustomReporterBlockMorph.prototype.reactToTemplateCopy =
+    CustomCommandBlockMorph.prototype.reactToTemplateCopy;
+
 CustomReporterBlockMorph.prototype.refresh = function (aDefinition) {
     var def = aDefinition || this.definition;
     CustomCommandBlockMorph.prototype.refresh.call(this, aDefinition, true);